you might want to make your own "wiki" type software inorder for it to meet your needs specifically, I am willing to help with this, I have a large amount of space with Dreamhost as well as a shit load of transfer. I am also very educated with PHP, CSS, HTML, etc. and have basic AJAX behind me. Just send me a PM and I can give you my MSN.
Edit: I could also write up some tutorials for the site too.