Hosting a website with user accounts and upload/download links

I'm hoping to make a website of my own that hosts custom maps for a game that has a user database. Where should I start? What would you recommend?

Here's a list of FOSS single-click upload webapps (within a larger list of self-hosted apps), it ought to be of some use.

Ok. How about the user accounts system? I want to have private message functionality, user uploads, and a ban system.