Looking for user registration system suggestions

I'm looking for suggestions for some web-based user registration system that gates downloads of a free-for-now in-development game. Eventually the game may be sold, but for now I am interested in building a community by releasing early builds for free so that people can watch the development process and I can get feedback early.

I'm not sure what kind of system might be available. I don't want to use anything like a Steam front-end. I want people to go to my development page, which is a Word Press site, register, log-in, and then be able to access the latest builds. It's also important that I be able to see which versions of the game each user has downloaded over the course of their account so that I can see who my key users are and how many.

At least on the user-facing side of things, Mojang's system seems similar to what I'd like. It would be even better if folks that register for my word Press Blog or bbPress forum can re-use that account information, but that's not super important.

I have someone that could develop a custom solution as long as I can set them in the right direction, but even better would be something that already exists.

In the past I've used Digital River to sell, but I've never put a free game on their service.

Any suggestions?

Thanks!