If you're doing Java work in a Windows work environment, I'm not sure you can do much better (okay, admittedly after about 10 minutes of testing), the VSS Plugin version 1.6.1 for Eclipse 3.1 over at SourceForge. Very smooth, incredibly intuitive integration with Visual SourceSafe.

I've tried a few times to teach myself to use CVS, but each time it's been less than, well, immediately intuitive. I realize that's not saying much, but VSS is and I've used it for years. So I recently eBayed a new copy (with reg number, of course) and started working. Thinking the VSS client would be easy enough to use with non-VB projects, I didn't bother checking for an Eclipse plugin first. Glad I did afterwards.