what's your best forum hoster? mine is vBulletin. cant get it because $160 is a bit much

I was just thinking about posting a topic similar to this. It's not necessarily a question of hosting, but of the client itself. I could use some advice on what to use for the website i'm planning. I like the look of Vanilla and SMF, or others such as those (mainly because they're still free but there are no ads).