There's an iPhone app that adds a cross processed effect to your images. It's called 'Cross Process' and it does add a really nice effect to pictures, a sort of vintage grainy feel

I know there are other more advanced apps out there such as hipstamatic that can have a similar effect but I think this effect is the closest to actual cross processed images I've come across

A few examples, the first shot is of Niamh and the second is a random piece of art displayed around Liverpool

Niamh by parrysite, on Flickr

photo by parrysite, on Flickr