Today I found very good, ad-free free forum hosting (http://www.makeforum.org/), but I can not install any mod. Do any of you know how to do this?
What about creating a phpbb forum?
I had problem implementing mods too, but phpbb simplifies the task.
The most simple and efficient to create a forum, imho ;)
If you haven't got much time, and want to see what the new phpbb3 can offer, just try it out on this host : free forum (http://www.forumotion.com)
Hope this can help!