I was definetly planning on using a PHP, MySQL driven forum. I was looking at phpBB2, IBF, and YaBB. If you have any comments on which are probably the least heavy on the webserver? I have give some though to purchacing UBB threads. I took them for a test drive and they where really fast and easy to use.. i was impressed. But phpBB seems quite speedy too.
As far as top side scripts. Well i know that can be a problem for slowing down sites, espcially poorly written ones. That is why on my main traffic site i am going to try and keep it as clean as possible. But i will inevidable use some. My other site, which is more of a personal site only gets about 30 unqite hits and about 200-300 page impression per day. More of a personal site so i don't think that will be too much of a problem.
My main traffic site i am possibly expecting as much as 20-30 visitors on the site at a given time. I am assuming most of the traffic will be via the forum. However, I want to start out kind of on the small side and upgrade if neccesay, because i am really not to sure on if it will take off. But i have a good feeling that it will, but i need to wait and see.