For teams I like to pick ones that go with the type of workouts I do.
LIke workout from home, or Jillian Michaels, Kettlebells, Tapout XT......
But I also like the challenge forums. I have one set up each month that you set a goal to lose 2-5 lbs each month and report as often as you would like for us to motivate you to reach it. There are a bunch of different challenges to choose from. Some are a biking challenge to post how many miles you have biked each month. I am sure there are running challenges, eat within your range challenges. Just need to find one that fits for you.
THere are Biggest loser TEAMS where there are teams and you try to get the highest percentage as a team per week. But they run about 10-12 weeks and there are sign ups at certain times.