Man, this one certainly took me a good while to find. (I work in payments processing, so I figured it would be easier).
There is a website, the Federal Reserve E-Payments Routing Directory, which provides this data in a fixed-width column format, and they provide the file format so that you can parse it, as well. I'd advise against re-distributing this information, though. Routing numbers and the scheme used to create them are considered copyrighted works by the American Bankers Association, and you don't have license to distribute their copyrighted material.
Because this data changes fairly often, you should check the site often for updates.