Haiku
Haiku is a desktop OS that will be binary-compatible with BeOS R5.Goals:
- Administration free
- Easy to use (e.g.: less options, better defaults)
- Free and Open
- Fast even on older hardware
- Powerful enough for the most complex uses
- Exciting to use
They have an interesting subproject called Glass Elevator that gathers new ideas for future releases: see their mailinglist.