You can make an avatar a la Scott Pilgrim, on the Scott Pilgrim Avatar Creator which is part of the publicity for the upcoming movie Scott Pilgrim vs the World. Here's what I came up with.
Meez, MyPictr (which seems to be a quick cropping site for your own photo), Gizmoz, My Avatar Editor (in the style of Nintendo's Mii characters), Simpsons Avatar (and a game, apparently), Zwinky, DoppelMe, and WeeWorld. I found these and more on an old Mashable post. At least one link I tried was dead.
I've used Meez, DoppelMe, and WeeWorld and they're cute. Meez is nice and I have one of my Meez avatars on my photoblog, Creative Endeavors.
Other goodies include this South Park avatar creator, South Park Studio, abi-station, eLouai Dollmakers, Hero Machine (I've used this for Shelly's Comic Book Shelf), Girls Inc., and Reasonably Clever (home of the Blockhead avatars, check out the Mini-Mizers dropdown menu on the top nav).