An open hardware and software platform, Octobits attempts to recreate the aesthetics of the early eight-bit computer age using cheap, powerful, and readily available modern components.
LoseThos, a free, 64-bit, multicore, PC operating system designed from scratch -- not a Unix. No bloat. Boots in 2 seconds. Comes with games, C compiler, tools and lots of demos of the API! Test-drive or install -- it is a live CD.
xizero is a 3d enhanced vertical scroller/shooter. It will run under linux and possibly windows and is a complete software renderer. More at: http://atcrosslevel.de