Frenzy Bulletin Board is another successor to fireboard, and features proper groups creation and permissions, which is kind of nice. The big problem is that they don't have as many templates and whatnot as kunena, right now. Check it out here:
www.f-bb.co.uk
Agora is also quite feature rich, although I wasn't able to get it working 100%.
www.joomlame.com
JFusion is also quite good, because it can integrate phpbb, smf, and more. It isn't quite as integreated into CB, but overall I'd say it's a great piece of software.
www.jfusion.org