Website forum system?

[DGath]

Need to recomend a forum system for a friends website. I'm fond of vBulletin's newest version, but it is $160 lifetime license and I'd rather go cheaper, if not free. Any suggestions?

 

[Nohr]

phpBB and Invision are a couple of the most popular free php/mysql forums.

 

[cheapherk]

I use Proboards on my website. The nicest free one I've come across.