Make sure you're also running Linux as your desktop machine. You'll be able to run almost exactly the same environment as your server, and it's a good way to be able to play around with all the different things available to you in that environment.
I wouldn't have recommend it about a year ago but nowadays it's caught up with others quite nicely feature wise, is very fast, supports snapshots and USB, and is completely free.
If you're only ever on a Mac, I vote VMware Fusion, but if you're going to change vm host environments, I'd suggest VirtualBox.
Jump feet first and use Linux as your main OS. If you are doing development work, it can easily surpass Windows, and is comparable (or superior) to OSX as well. Of course, this doesn't apply if you are doing graphic design stuff, however, Windows can live inside a VM for that sort of stuff. If you are doing web dev, you'll need a VM for Vista/Win7 and for XP anyways.