People often ask me what app/s they should use to get started drawing on their iPhones, iPads, iPod Touches, and other touchscreen devices. I've only used Apple's devices, so the bulk of this information is for 'iDevices'.

However, there are Apps for other devices, too. Here are the ones I know about. For the Surface: Fresh Paint. For the Android: Artflow Studio, Sketchbook Mobile, Photoshop Touch, Pixlromatic, Bamboo Paper, Little Photo, Paint joy, Corel Painter Mobile. For the Galaxy Note: Infinite Painter, Paper Artist, Kaleidoo, Crazee, Penman, Pattern Maker, Vector Artist.

Please leave me comments if there are other Devices & Apps I should add to any part of this article.

iPhone, iPod Touch, iPad
Here are some recommendations for beginners, from simplest to more complex, followed by recommendations based on which traditional media you use, followed by a more complete list of all the apps I use. Fortunately Apps generally cost less than USD 5 so it doesn't break the bank to try a few to find the ones that are best for you.

Zen Brush
is a very gratifying and easy to use program that is sort of like drawing with a brush and sumi ink - and has some of the same limitations (ie no color, etc). You do have a slider for line thickness and a couple levels of transparency, an eraser and one undo. Great for quick sketches. You can see some zen brush work here: www.flickr.com/groups/zenbrush/

Drawing Pad (iPad only) is also very gratifying and easy to use and any young people who have access to your iPad will likely enjoy it, too. You pick from familair art supplies like crayons and markers, then click on the one with the color you want to draw with and drag your finger across the screen to draw. In the most recent upgrade you can turn on advanced features like being able to zoom in and select any color you want, not just the presets. I don't know of a Drawing Pad group but you can see some of my pieces here: www.flickr.com/search/?ss=1&w=7540599%40N08&q=dra...

Art Studio, Brushes, SketchClub, Sketchbook Mobile, Procreate I think of these as 'Swiss Army Knife' art apps. They all have alot in common, such as lots of different brushes to choose from, many layers, millions of colors. There is no 'one look' of art made with these apps, just like each artist using a pencil, the artist's style determines the look more than the app does. Most artists will usually settle on having one or two of these in their toolkit. The features are slightly different. For instance, Art Studio has more Photoshop-like features such as for selecting and transforming, Sketchclub has vector, procedural and text brushes as well as 'paint' brushes, Procreate allows incredible flexibility in creating your own brushes by importing photos to use as texture maps. They also each have different interfaces - and you'll only know which is best for you by trying them.

To see a selection of works made strictly on the iPad check out this flickr set: www.flickr.com/photos/juliakay/sets/72157625309740035

Art Apps by your traditional media preferences
Acrylic or oil paint: Art Set Pro (be sure to get Pro for the great paint!), Artrage, Inspire, Pollock (may no longer be available), Sketch Block, Wasabi.
Watercolors: Artrage, Auryn Ink, Sketch Block, Colored Pencils (with add water feature), Henpitsu. Artrage has watercolor brushes but they aren't nearly as good as their oil brushes. Auryn Ink gets the wettest effects, interface is a bit tricky.
Pastels, crayons: Artrage, Drawing Pad, Typedrawing, Art Set/Pro, Graphite
Ink brush: Zen Brush, Henpitusu, Eastern Artist
Pens / Pencils: Pen & Ink, Graphite, Colored Pencils, Sketch Club, Omni Sketch, Procreate, Drawing Pad
Charcoal: Procreate, Graphite
Collage: Finger Design, Procreate, 2D, Juxtaposer
Woodblock Printing: Ukiyoe (It's a really fantastic simulation of the whole process of block printing and an excellent tool for learning before cutting into real blocks - but alas may no longer be available.)
Carving/sculpture: iDough, 123sculpt, Sculptor

For children: Drawing Pad, Drawing Carl, Art Set, Foldman

Some More Information About Some of the Apps

Art Set Pro My current favorite for thick, fluid painty effects but it just came out 11/2013 and there have been some reports of crashes without saving your work, so save and duplicate frequently. It is a tad pricier than some of the other Apps, so if thick paint isn't your thing, this might not be your App.

Artrage I don't recommend this to start but it also does a great job of simulating paint effects, from thick oils to bleeding watercolors, to scraping a palette knife through paint squished out of a tube. Artrage is available on pcs &, macs, as well as iDevices. You can see Artrage images here: www.flickr.com/groups/artrage/

Art Studio Very full featured App, the one I think is most like Photoshop. Lots of things you can adjust which means lots more sliders and interface things to learn about. Lets you resize layers, select an area to cut and paste, including a magic wand type tool, good set of layer blend modes, and fun brushes with lots of customization. Art Studio group here: www.flickr.com/groups/artstudioimages/

Brushes
used to be my fave of the basic, full-featured apps for artists, but in the long wait for an upgrade, I came to prefer Procreate. Brushes 3 still seems a little weak by comparison to Procreate. Nevertheless, you can select from millions of colors, at least a dozen brush types, sliders for line thickness and transparency, import a background image if you want, work with layers, if you want, etc. Quite a variety of Brushes images can be found here: www.flickr.com/groups/1238939@N25/ (Others swear by Sketchbook Mobile, also an excellent App, but I prefer Brushes' interface)

TypeDrawing
A personal favorite, it doesn't emulate traditional art materials at all - unless you're insane enough to try drawing by moving a piece of paper around in an old manual typewriter. In any event, this App lets you draw with type, which of course is convenient for adding text to images, but also makes a really great texture rather like pastels if you draw over areas with it, allowing the type to overlap and become somewhat illegible. It also has a feature I haven't seen anywhere else, which allows you to select a range of colors to draw with, so for instance you can select a range of saturated warm greens to block in trees and darker, less-saturated cool greens to block in their shadows. This also allows you to get alot of color without constantly having to go to a color wheel to get another color, while still giving you quite a bit of control. My TypeDrawing pieces can be seen here: www.flickr.com/photos/juliakay/tags/typedrawingapponly/

A more complete but less detailed list of Apps for the iPad, iPhone and iPod Touch.
If there's a link, it will take you to examples of work made with that App.

Full-featured Drawing
ArtStudio
Brushes
Procreate
Sketchbook Mobile
Sketch Club

Quick Sketches
Finngr
Inkling
Paper by 53 (but beware the in-App purchases)
Sketchtime
Vellum
Zen Brush

General Purpose Painting:
Artrage
Art Set PRO
Auryn Ink
Henpitusu
Inspire

Sketch Block
Wasabi Paint

Vector Drawing

Skribl (hot off the presses 12/2013!)
Quill (No updates in a long time)
PaintBook
Inkpad
Adobe Ideas
MiniDraw
Sketchbook Ink
Sketchclub (has a Vector tool but saves pixels)

Procedural (The App draws with you)

ASketch
Flow Paper
Harmonious
Omni Sketch
Qvik Sketch
Sketch Club
Wasabi (The brush that richochets)

Specialty:

Calligraphy
ColorTilt
DecoSketch
DoodleBuddy
Drawing Carl
Eastern Drawing
Finger Design
Fountain Pen
Inkling
Magic Brushes
Paint for Cats
Pollock (May no longer be available)
Rothkomatic
Scribblify
Sketch Share
TwoToJazz (In-app purchases necessary to get all the features). An interesting interface where you use two fingers to draw, and thus can make the line thicker and thinner without a pressure sensitive stylus. However,most of the brushes are flat rather than textured or painty.
TypeDrawing - More than drawing with type, you can draw with ranges of colors, and build up a texture quite like pastels.
TypePlay
Vellum
Ukiyoe (May no longer be available) - A truely fantastic simulation of block printing, the only in-app puchase you need is the full toolset.
Wasabi

Not used that much but sometimes:
Carve the Copper Relief
Sketches
iDoodle2
iDoodleIt
DoodleKids
KidsPaint No. 2
SpinArt
Squiggles
SketchMania
Sketchinz
Scribble Lite
ScratchAway
Sculptmaster free
Wooly Willy
Photoforge

For manipulating rather than draw/painting:

NPTR
DXP
Juxtaposer
PhotoTwist
PS Mobile
ArtCamLite

For generating rather than draw/painting:

SpawnLite
Vihgo

I don't recommend these:

Flipbook Lite
Layers (no longer updated)
Light Show
Oil Canvas
Graffiti Spray Can
Magic Paint
Steam Draw
Sketchwalkers
ZeusDraw

I haven't tried yet:
Foldify
iTracer
Water Color Pencils

Learning more and finding other mobile digital artists.
There's a great international mobile digital artist community that overlaps flickr, ipernity and facebook. You can find the community in some general and many app-specific groups. Search groups in all three locations for iPad and Mobile.

In addition, everyone using their finger (instead of a stylus) gathers here: www.flickr.com/groups/875908@N23/

This group is specifically for iArt how-tos: www.flickr.com/groups/1633745@N23/

Here are some thoughts about the different artmaking possibilities on mobile devices: 1. You draw. The device is just a different kind of pencil, ie you use your finger to draw a mark just like you'd use any other art supply. It takes exactly the same amount of eye-hand coordination. Apps like Brushes are in this category. (Of course it is easier to trace on the iThing but nothing stopping you from tracing with traditional materials, too). *Most* of my iThing work falls in this category.
2. You and the device draw together. For instance, you draw with your finger over a photo, and where you draw, and perhaps the speed with which you draw, causes a mark to be made which is 'extrapolated' from the photo. Apps like nptr are in this category. I sometimes use these as part of the drawing process. I think Patricio Villarroel is a master of using these, epecially nptr.
3. The device draws from the photo under your direction. You pick a photo and apply different filters and effects from different Apps, usually to the whole photo, but sometimes directed by your finger to only a specific area. effectTouch is in this category. I usually apply the effects to my drawing, rather than the original photo.
4. The device generates abstract imagery under your direction. Either by following your finger or just running on it's own, different algorithms in different Apps generate different abstract images on the screen - you often have control of a bunch of parameters, such as color set, line width, etc. Meritum Paint is in that category. I'll use these to generate interesting forms, shapes and colors, which I then use as an element in a piece - either as a background or blended layer, etc.