It's a T60 with upgraded CPU (T7600), second hand 60GB SATA II SSD, 3GB RAM (limited due to chipset bug), ExpressCard with USB 3.0 and a 9-cell battery which lasts for 1/2 hours.
I spend around $100 for this machine in total, only $25 for the T60 itself.
I'm not using this particular machine because the specs are so great, but because I found it on Ebay and it was painted yellow. It's such an awesome thing. It runs Debian with XFCE4 fine, but websites like Facebook in Firefox isn't that fast. For development purposes it's perfectly fine.
I'm thinking about upgrading this machine with a motherboard from a T60p with a FireGL GPU one day, but I have to research if that would work.
You could take the same route as I did, but if that's too much work I'd go for a X201 with SSD and 8GB RAM.