Allow users to browse different Collaboration spaces and join the ones that interest them. Allow ability to search, filter, and TAG Collaboration spaces and posts. Allow ability to pin favorite Collaborations. Allow Collaborations to show most active users/ gamification. Allow notifications (daily, weekly, monthly, real-time) for Collaborations.
You might also want to vote on: LMS-I-313, LMS-I-118, LMS-I-2136, and LMS-I-2062
These ideas are all similar to this one.