OpenBeOS - binary compatible with beos (renamed to "Haiku")

BlueEyedOS - source compatible with BeOS and linux

AtheOS fork with BeOS aspirations

beunited.org - news about beos clones, and plans to sell beos clones (?)

BeFree - source compat, which may be broken in future releases. Runs overtop of FreeBSD and Linux. Doesn't use X11.

Dano and PhOS are probably illegal