In reply to OriginalEXE.

I've used a few plugins for this in the past. I've previously used Taxonomy Metadata by mitcho and sirzooro. It is very barebones though. I've also used Types plugin by OnTheGoSystems. It adds an admin interface for taxonomy meta but I personally found it a bit cumbersome. The best solution I've found so far is Advanced Custom Fields by Elliot Condon. It adds taxonomy metadata functionality and has a very nice admin interface.