After I posted the Arch Linux distributions list I cannot resist to post a list with distributions dedicated to the openbox desktop environment.
Arch Linux based:
Sadly probably deprecated.
Crux Linux based:
No live cd.
Slackware Linux based:
Not openbox-only but they put a lot of effort in their openbox edition too. No live cd.
Heavily inspired by Crunchbang and Archbang.
PCLinuxOS has MiniMe:
I know lists are a bit stupid somehow. But for openbox-fans like me it might be nice to try and learn from each one of them.