Thanks for the input guys. By the way, my site is nothing like what it will be. I basically use it to test things out, but it's nothing near the real deal (if you check it out, disregard everything on the site). I'm not planning on giving users web space for just anything. The users will be able to upload images only, and each person's folder will max out at say 5 mb. What I'm basically doing is setting up an image gallery that is integrated with flash, and it loads folder names and images. About security...I can get a dedicated IP, and I'll try to read more into the scripts about security.
In response to Damian, I know HTML and flash well, but I really don't know how to write php, cgi, etc. I only know how to implement them, and I don't plan on leanring them.