i run 3 forums 2 on createphpbb and one on freeforums, i have to say freeforums are the best of the two. Although they recently had problems they were still very helpful and the features they offer are really good for a free forum host. I want to move my other 2 forums over to freeforums, but createphpbb are ignoring my requests for a data back up to transfer.
I'm currently with LunarPages (which allows for you to use your own forum software (of which I downloaded/installed phpbb3) and I have to say it's excellent. Now if only I could get the traffic I want... lolz...
The only thing good about invisionfree i think is the speed and the amount of skins... I can think of many that offer much much more featurewise like http://ipbfree.com and especially http://jcink.com/
When they were still accepting free forum registrations, Exocrew was an exceptional free forum host. They provided FTP and phpMyadmin access, unlimited hdd and bandwidth, and decent support, and pre-installed either phpBB or IPB, all for the price of a single small banner on the bottom of the forum pages.
I started a new forum with jcink.com. It's Ipb 1.3 but they have installed just about every mod there is. I also have a forum on invisionplus.net with over 300 members but that host has really gone down hill lately with their server problems. The best part was that you could install a lot of skins and the ads were at the bottom.
i like bizhat for php as it has no ads but ifs good for ipb to. however more features for ipb you would want ipbfree and more php features you would want freeforums.
http://www.myfreeforums.org is the best forum provider which its free to use, and the service on the support forum is very helpful and normally get a reply in minutes, ive been using it and the forum uptime is also very good, there are ads, but these can be removed for a small fee!