About 10 months ago, I posted a lazyweb request for a blacklist-based comment-spam solution. Only 2 days later, Jay Allen posted a solution that pretty much did exactly what I (and many others) needed. Ever since, he's been adding more and more features to aid in the fight against comment spam and even started maintaining a master blacklist people could sync up to. As far as I'm concerned, out of the hundreds of available MT-plugins, his is by far the most useful.
He's now almost ready to release MT-BlackList 2.0 and from what I can tell, it's going to be the must-have plugin for Movable Type 3.0. You don't have to take my word for it though - six apart just awarded him the grand prize in their "Plug In To Movable Type 3.0" Developer's Contest: a kick-ass Apple G5 dual 2GHz system with a 23" cinema display.
Congratulations Jay! you absolutely deserve it.