My favorite is
Extrapounds.com, of course
It works for any diet - also ex-phensters to maintain weight, share experiences, participate in the support groups and have your own blog to share with the community.
Also there are funny trackers, very visible weight log graphic to see your evolution during the time, food log to count eaten calories, activity log to count burned calories when exercising, photo albums and other useful tools.
Have a look
They will have a new image and friendly use in few weeks!!
Susanne.