I started using TortoiseCVS on the advice of a customer. TortoiseCVS extends the Windows UI shell to add CVS functionality as right mouse click menu options - really useful!
I have been looking for similar Windows shell extentions for adding explore Java JAR file options. The best that I have found is Raphaël Mounier's ICEOWS package. I used to change a JAR file's extension to .zip, explore, then change it back - a waste of time.