Fantastic Lomo photo effect that you can create using Photoshop (and these instructions). Lomo photography is basically photography with very high colour saturation, and I think it looks amazing!
For a modern comic book look (I love this style!) you can follow this tutorial to create a photo like this:
And lastly, for a classic Andy Warhol effect (would be great as a present for a best friend or family member), you can go here for the guide.