I love hacking around on my N800. I have a multiple-boot setup with various flavours of the Tablet OS (and Debian) running in different partitions on my my SD card.

My most exciting project recently has been getting Debian applications (like Gimp, AbiWord, OpenOffice, Iceweasel, etc) running seamlessly on the tablet using a chroot, a nested X-server (Xephyr) and a light window manager (IceWM).

Please see http://www.internettablettalk.com/forums/showthread.php?t=21629