I am a big fan of Photoshop, and so are a lot of other artists out there. Worth100.com hosts regular contests to encourage submissions on a particular topic. The photos are such fun to look through. People can make the added elements look flawless. Sometimes, I would swear that it the image is real, if they weren't so absurd. I am quite impressed. I have a feeling the key is in the shadows. The quality of the shadowing is how you can tell beginer from an expert. I think it has a lot to do with integration too. The lines blending the new element and the old have to be the same level of intensity as the rest of the photo. That is where a lot of people go wrong. I'm also amazed by people's wittiness for the contests. He he. This site makes me smile. Maybe I'll submit something someday.
A few of my favorite advanced Photoshop contests include:
Death takes a Holiday
Planet of the Apes
How do you hide an elephant?