I manage a challenge group site on MSN groups, was originally started up by someone else off weightwatchers but they roped me in to help then b*ggered off lol We're in week 6 out of 8 atm though but I'll be doing a new one starting 12 January so will see if people on here want to join in then.
Only problem is MSN groups is shutting down in february lol I've tried starting a new group on their suggested alternative multiply but it needs tweaking. If anyone knows of any decent sites which support groups let me know please!
It tends to be slightly more organised (excuse me!) rather than having threads I do weight loss tables with groups of ten, putting everyone's loss in each week etc then have message boards for reporting losses and stuff.