Plan 9 from Bell Labs runs on the sheevaplug! It was announced a few months ago on 9fans, the Plan 9 mailing list. Relevant links (to Plan 9, the announcement and instructions) can be found on the Plan 9 page for the openplug wiki:
http://www.openplug.org/plugwiki/index.php/Plan_9Note that setting this up requires some knowledge of Plan 9, so this is not for everyone.
