Heck, even as I was messing about with my own Arduino, I was scared to burn out my PC through my USB port. I burnt out a few LEDS, because I'm rubbish with current-resistance calculations. Got that burnt plastic smell, and started sniffing around my PC. Luckily for me, it was just the LEDS. Almost had a heart attack.
Sounds like you should consider buying yourself a Pi kit... :P Rig it up on a wireless connection and SSH or remote desktop into it, and you have a fully isolated system that will only cost you a little bit and be easy to replace if/when you set fire to the whole thing.
May also want to get a ceramic topped work bench just to be safe. And maybe a fume hood. Magic Computer Smoke is probably not good for the lungs. (Okay, maybe going a little far with it, but non-flammable work surfaces are kind of nice, assuming you remember to not clutter them with papers.)