http://www.moddb.com/mods/fragging-free
A very large, but very fun and addictive mod add-on for Doom 3: ROE expansion. It brings back everything Doom 3 wasn't. Its original Doom for the new millienium as far as I'm concerned. The intro level (not tutorial) alone is a sight to see. Enjoy!
Fraggin Free - bloody awesome.
If I had Doom 3 I'd check this out but I don't yet.