Thinkpad T41 and Knoppix
The Knoppix bootable Linux distribution (where you don't actually install Linux on your hard disk; you boot Linux right off the CD and it uses a ram disk for temporary storage) works on my Thinkpad T-41 laptop!
And the T41 has some space left at the end of the default partitions that you can use to set up a real swap and home directory, without having to remove Windows.
It even detected and configured the wireless network interface and sound!
This is an awesome way to play with state of the art Linux stuff without having to commit. Download it using BitTorrent.