[kunai]

It's kind of the same deal now with the Raspberry Pi, except for the fact that it uses RISC and not x86. It's a great tinkering platform.

Now, if only somebody would make a ring-0 OS for ARM... Now THAT would be fun.

[pjmlp]

You mean like Active Oberon?

http://www.ocp.inf.ethz.ch/wiki/

Not sure how workable this version is, but you can check on the forums,

ftp://ftp.lrz.de/transfer/BlueBottle-A2/ARMRelease.zip

You just need to enjoy using Pascal syntax languages for system programming.

[nitrogen]

There is FreeRTOS (http://www.freertos.org/).