Check out DotNetNuke (
www.dotnetnuke.com). The community version is free and has a repository module that will do what you're looking for. The documents module is a little more simple, but will work as well. DNN requires an ASP.NET/SQL hosting plan. If the included modules won't work for you, check out
www.snowcovered.com for a ton of 3rd party modules.
If you're a developer, there are quite a few resources to get you started with developing your own modules in ASP.NET/VB (please no C# is better than VB arguments -- I didn't pick the language).
-SDT