Developing on JBoss, and using the hot-deployment will get you the PermGen OutOfMemory errors sooner or later. I was happy to find this solution some days ago.
Just add this line to the run.bat:
set JAVA_OPTS=%JAVA_OPTS% -XX:+UseConcMarkSweepGC -XX:+CMSPermGenSweepingEnabled -XX:+CMSClassUnloadingEnabled -XX:MaxPermSize=256m
The inventor claims there are still problems with his solution but I never saw the PermGen again after I added this line !