What types of forum software's out there allow you to pick a plan that gives you a free domain with it? Like one of those www._____.whateversoftware.com
Those are the kinds of hosts that you want to avoid. Oftentimes, you're plagued with forced ads, slowness, and ease of hacks. Instead, why not get hosting yourself (you can get away with a free cPanel host if you're just starting up) and run your own phpBB, MyBB, SMF, or whatever forum. Here's one on the top of my head. http://www.excelledhosting.com