FreeForums - A free forum hosting which currently has no ads...

[hamradio]

It uses phpbb and right now they say it is no ads, unlimited bandwidth (although my opinion is nothing is unlimited), and other misc features.

FreeForums.org

[f0dder]

...and which will eventually turn into a free tons-of-ads-and-slow-as-molasses versions, and a payware version.

Bandwidth is hardly ever a problem, so "unlimited bandwidth" doesn't mean much. They'll need unlimited memory and processing power for the database server though, which is a lot harder to guarantee. Ever seen how forums hosted on shared boxes run, once the host reach their (oversold) capacity?