Rainbow over Denby Dale 

I was actually on the retreat when I shot this, the rain was coming in sideways, I was soaked and on my way back to the car.
I shot hand-held (had given up on tripod, too windy) while hand holding a grad ND Cokin filter.
Tweaked contrast and saturation in PS (and cloned out all the raindrops that were on my filter) that is about it.