There was also "Mastodon Linux"[1], an attempt to both get rid of most of the GNU userland as well as stick to the a.out format (for binary compatibility and glibc-sucks reasons). Always thought it was kinda interesting, but pretty dead due to basically being a one-man project (by David Parsons, nowadays mostly known as the author of the discount markdown parser).

[1] http://www.mastodon.biz/