That's a tough question to answer without better understanding the technology, but it's critical that there be an easy and obvious way to interact. When such interaction does occur, highlight it - "recent posts," "recent profile comments," etc.

Adding a forum element if you don't have one might be another way if you can drive your members to it.

Hey Rogerd,

We have all of the above. Users have their own customizable profile, they can post comments, videos, add friends etc. Latest posts, members, downloads etc are all highlighted.

Perhaps I expect too much. Members are interacting, I'm just always looking for new tips and ways to improve.

Thanks for the response :)

I recently created a 'point' based system for my site. It assigns a value to certain actions and at X number of points the user reaches a certain 'level' on the site.

It has done nothing but increase user interaction with the site. Even though the 'level' gives the user nothing more than bragging rights.