Create an avatar, a cartoony version of yourself, for profile pictures. Set a time limit for yourself...these are addictive! Some have a "randomizer" option which is a fun way to see what's possible in each program.
Dopple Me (registration required)
Pick-a-Face (as guest or register)
Face Your Manga (registration required)
Want more? See here
Tech Productivity Tools: Add your ideas for "Harnessing" the Web