As for me, I use a 1st gen black MacBook w/Leopard, added a bigger HDD and aftermarket RAM to 2GB. I use a Logitech V470 bluetooth mouse which I carry everywhere, and I've got a couple of bluetooth apple keyboards (shorties without the num pad) - one for the office and one at home. For external monitors I've got a cheap Dell 23" widescreen in each location.
For the occasional Windows mission (usually to load updates to my N95) I was using Win XP via Parallels, but my experience with the performance of the last few releases has left me wanting and I'm currently using a trial copy of VMWare Fusion.