Levent Gurses has a nice blog entry on Remote Debugging with Eclipse. I was able to use his instructions a couple months ago to attach to a remote instance of WebLogic (8.1 SP4) to debug an application. The beauty of his instructions is I had it all working in about 5 minutes. Yesterday I realized you could use the settings in *any* application server, and remotely debug it - or at least you should be able to. Today I noticed he added instructions for Tomcat and JBoss. Good stuff - thanks Levent!
Here's the settings you need in your startup script - just in case Levent's blog is down the next time I need this info.