[bartonisium]

Good advice here, you guys have covered most of all I have to say, lol. Also, I would consider a LAMP setup [Linux, Apache, MySQL, PHP]. You can use just about every CMS / forum software, WordPress, vBulletin, Drupal and some others I am not familiar with.

I've found with web hosts that bandwidth isn't usually the issue. Generally most webhosts will give you more than enough bandwidth even on shared hosting plans. My bet is you will run out of CPU and memory before bandwidth.

Like the folks before me, I highly recommend going with a hosted platform, especially if you want to have even a small forum. I hope this helps.