software for forums

Hi,

I want to setup a forum. Ruby(RoR, Sinatra,…) would be my choice.
Does anyone knows a nice (not a 4 color ugly !grrr!) forum web
app? I really don’t have the time to write my own and unhappily would choose
PHP or .ASP or whatever. If you could give me a hint, that would be great. As
an alternative I can imagine an app which allows collaborative writing and
commenting, ACL would be nice too. ( lots of options or easy extensible).

So a big thanks to anyone for hints. (and yes I search
Google).

Cheers,

Chris

So far as I know, most good forum software allows control over the
appearance.

I've never really looked at what's out there in terms of Ruby forum
apps, but a lot of people use Beast. Disqus might also be worth a
look.

Best,