We just updated our SDAC Related Content plugin to fix a few bugs and to also add in some additional functionality. You can now choose to show related posts by tag or by category. (No longer just category). This is a great plugin for anyone looking for related functionality on WordPress, WordPress MU, or VIP hosting as it does not make any database changes and it uses caching.
Check out the forum for any support issues or leave any feature requests and we will do our best to add them into future releases.