For a couple of years a buddy and I have been trying to get a forum going. It's not a easy thing. Installing a forum is a piece of cake and so is setting it up.
phpbb is the best for free. It also has a great admin panel.
vBulletin is the best for cost but it has a ugly and messy admin panel. There is lots a support and mods for it though. It's what made us make the jump to it.
Actually getting members is solid though!
