Paper curl effect

whats the best way to make the paper curl effect?

I made it work but it’s lacking shadows in proper places (cause I can’t figure out how to do that) and it basically just uses images laid over one another so that it looks right. Any tutorials on how to make this work? I know learnflash.com has a cool intro where the main page does this when you rollover it and the page curls up to show the contact info. The paper kind of eases out and bounces like it is elastic as well…

Anyways, any good tutorials?