I'd try this page. There are lots of cool programs and you can look at the source to see how they do all sorts of cool tricks.
I use Webjeff's Filemanager on my site, and it works great. Best thing is that you can give people access to specific directories using passwords, and no FTP access is necessary.
Incidentally, both links are at www.hotscripts.com. Get to know that site well -- there are a lot of cool things there, and is a great way to learn by looking at source code of various applications.