If you run a wordpress site you may want to take a look at WPMU Dev. They appear to have some fantastic and powerful plugin to enable all kinds of functionality. I’m really interested in the Q&A and Snapshot (backup) plugins at the moment. Each plugin costs $19, but there is also a monthly subscription plan to have access to over 350 plugins.
WordPress Plugins – Guaranteed to work, always updated, top quality plugins. Beautifully coded, packed with features and easy to use.