[JakeGallagher]

For the most part with our team, we keep the members interested with lots of work. Everyone has a part that they can do, and the jobs are in PostIt notes on the front board of the classroom we work in.
We have meetings every monday and wednesday from 2:30 to 5:00, from 2:30 to 6:00 on fridays, and from 10:00 to 5:00 or 6:00 on saturday and sunday. Generally, only the people what aren't involved with other stuff show up for the weekday meetings (we have 2-5 people there usually).
Weekends we see most, if not all the team. Every weekend meeting one of the mentors brings in food for the team (recurring pattern?) and we all break for lunch at the same time to have a team update session. This time is spent with the members chatting with each other, about whatever they feel like. Often the subject is what we've been working on that day but no matter what it is, the conversationbuilds bonds within the team members. Some members only get to see much of each other at meetings because they don't have classes together or they live in different towns (our school serves 7 towns in the area that don't have high schools).
I guess, to keep people interested, we always have work so they don't get bored, we keep good food for the long sessions so the members stay energized, and we let the members bond with each other. Friends work better together than people who are merely on the same team. True, not everyone will be best friends, but there will be people that come to work mainly with other people.