This is a common sight in many online communities: 
Some thoughts: 
Frequently update your forum to make what members want more accessible. Be reactive (and receptive) to what’s happening in your online community.
Some thoughts: - Organize your categories by popularity. Most popular to least popular.
- You should remove categories with no activity(note: when you do launch a new category – be sure to accompany it with a big promotional push). Media we love, classified ads and everything else can go.
- When you see a popular discussion taking place in your community, or a frequently mentioned topic come up, create a category for it and mention that to all members.
Frequently update your forum to make what members want more accessible. Be reactive (and receptive) to what’s happening in your online community.