Some plugin-ideas that could be nice (not sure if they are all possible atm):

• Pinging the users when a new unread posts or chat message appears
• group chats? (public to everyone or with invites)
• Registration has to be accepted before allowed to be logged in
• Adding tags to topics (different from categories). Posts can be tagged with multiple tags!
• Some sort of tagging of users under their avatar. Like novice, ... These should be configurable by the amount of posts by that user + being able to be set per user manually (by the admins).