Hi,
for those not checking SlashDot - the TU Dresden's Operating System group
has released some of their work in the form of a demo CD. It is a nice
L4 microkernel-based OS, mostly licensed under GPL.
http://demo.tudos.org/eng_about.html
The ISO is 118MB, they provide a .vmx for VMware player, they also show
how to use qemu to boot the thing.
Have fun,
Eric