As many as you need. I am not a full time programmer, but in recent months I have gone from 2 desktops (one for audio/video and one linux desktop) and a work l

As many as you need. I am not a full time programmer, but in recent months I have gone from 2 desktops (one for audio/video and one linux desktop) and a work laptop to one personal macbook pro with an Ubuntu VM, Slicehost (Ubuntu) and EC2. Works fine for me, at least till I get gear acquisition syndrome again.