There are two ways to gain access to ScottSS's extensive galleries of first-class fake celebrity nudes: either fork over the (very reasonable) membership fee, or virtually undress the likes of Mischa Barton and Scarlett Johansson and win one of the the monthly photomanipulation contests with your own original submission. True, you'll be up against some pretty serious competition, but the free Photoshop tricks and techniques on the site will at least give you a head start for the next round.

Fake/Off Monthly Celeb Faking Contest and The Take Off Contest (info and tutorials @ scottss.com; more tutorials here)
Previously: Fake University, Morph How-To