The only other free forum software I've used is MyBB www.mybboard.com It doesn't have a lot of mods/hacks, if thats one you are after you might want to look at something other then MyBB.
well there is also another free forum software IKONBOARD.you can search it on google to get the exact result.
yah, i vote for phpbb too - for free forum scripts, that is. vbulletin's the best overall - but it costs $$$.
i have seen quite a few webmasters say that punbb is a better alternative. Also there is SMF too , no ? I have no first hand experience as i have not used them more than 1 week at most .
THen for my new forum, went to punbb and I like it better. Try it for a bit, and see if it is what you would want to have always. Or until sometime better comes out.
don't dismiss minibb - it is lightweight, simple to integrate, fast, simple to skin, great templating system, several plugins/mods available. The last time I installed it, it took me only about 20 minutes to install and integrate into my site - brilliant for smaller sites (sites that expect to have less than 100K posts)
Are these all more secure than phpBB? The only reason I am shying away from phpBB is security issues Thanks
As you already know VB is best! Its such clear choice when it comes to forum softwares. If you can afford to start with $$ then you can take leased version and I belive (you should confirm with VB though) purchase the owned copy within two months time. That would give you enough time with your forum to see if its going in right direction. If you are keen on free, I have so far used SMF and its pretty decent. You can always migrate to VB, but you never know how migration works.