My first project (and thankfully not my last), ByteHoard grew from a small unknown open source project to a slightly larger, largely unknown open source project.
It was an online file storage system, albeit as a package you install on your own server rather than a complete hosted solution. It was written in PHP (and varying levels of quality) and has survived pretty well through the years, bearing the brunt of my learning mistakes.
I did at one point start work on the next version of ByteHoard, but that development is now indefinitely on hold, while I pursue other projects. If work ever does return, it will not be in PHP.
I did briefly revisit the ByteHoard codebase to extract a one-time-upload link system; the code obtained works, but it's not really production quality. If you'd like a copy, email me.