w2box - Web 2.0 File Repository for PHP is actually a little more than just an upload script, it's a full-blown file management script. It shows you what has been uploaded, allows you to view/delete files that have been uploaded and allows you to upload with a progress bar. (DISCLAIMER: After being wrong on the last progress bar discussion I do not present this as a REAL progress bar but in my exhaustive testing of uploading a single file to the demo site, it did seem to be accurate.) Aside from the fact that the progress bar uses a cgi written in Perl (why? Why? WHY?) it does seem to be a pretty cool (and free, did I mention free?) piece of code.
The rest of the brief post mentions some of the features that w2box has, including direct deletion using Ajax, and the ability to protect/hide uploads easily.