Drools 2.0 beta 18 is out. It's faster, more stable, and slightly easier to use. Still very weak with debugging support though.
FYI, Drools is a nice open source Java rules engine which I have been using to build a forensic analysis system. I ran into some irratic behaviors over the weekend but this update cleaned up the problems. Whew. That saved me the trouble of wandering inside stranger's code which can be messy.
Oh, Creole is another helpful Java tool you can use when you find yourself inside other people's nightmares. It shows a zoomable diagram (not UML mind you) of Java code. The zoomable part was implemented using Jazz. If you are interested in ZUI (zoomable UI), skip Jazz and head directly to Piccolo. It's open source and there is a .NET version as well.
I have been doing too much Java lately and not enough .NET and Win32 stuff. It feels like a side of me is getting rusty like the Tin Man.