I think I have it figured out. there is a good explanation here: Setting Up A Virtual Host in Apache

This only answers half my question though. I'm currently using a forum in one of my site. I have plans for two other sites that will also have forums. So far, i like this particular forum (Simple Machines Forum) however, it is procedural and all fits in a sub folder.

Question: Won't Zend Framework thing that domanName.com/forum is trying to reach a controller directory? Is there a way to have such a forum system implemented along side a site on Zend Framework?

Certainly, the reason for Zend Framework is to implement things such a forums in a site. If I were 20 times more competent at this stuff I'd think about writing one. But until then an open source forum like SMF is pretty handy and secure.

Any suggestions?

This forum is a vBulletin but it's on a separate URL from everything else...