BuddyPress.org

I prefer Slicehost over MediaTemple. Given your stated requirements, a 1GB slice will work fine. You\’d probably even be okay with a 512 slice. In fact, you can start with 512 and upgrade if you find it is insufficient.

By the way, here is a Slicehost forum thread you may find useful: http://forum.slicehost.com/comments.php?DiscussionID=1082&page=1#Item_0