From Developer Tutorials, there's a new tutorial posted about creating a file upload script combining PHP and MySQL.
I much prefer to upload files to mysql instead of saving them directly to the file system. I can run database backups/mirrors that are much easier to manage then if files were placed on the file system. Here are the simple scripts I use to upload files and a script to stream the file back to the browser.
The tutorial is mostly just the code for the simple application - the MySQL table structure, the PHP code to handle the file (including the insert into the MySQL database) and the code to download the same files.