I would also add Macbook Air with Parallels/VMware/etc. running Linux. Price is in the $900 range for an entry level one, build quality is great, and battery life is amazing. Running Linux in a VM is nice because you get working power management, touchpad, etc. from the host OS without any screwing around.
I'm also running Linux (XUbuntu) as my development environment of a MacAir. It's been pretty sweet so far. The only thing it could use is more memory. A 32GB option would actually be nice in the MacAir but there might be hardware limitations for this.