The Kindle is already able to read more than just Amazon DRMed content, it can handle a number of formats.
There are converters available from Amazon and/or Mobi for pdf and doc files.
Non DRM Mobipocket format is already supported on the Kindle - just drag and drop.
The Kindle has many flaws, but it does allow you to read a few different non-DRM formats.
A revolutionary portable reader that wirelessly downloads books, newspapers, magazines and blogs to a crisp, high-resolution electronic paper display that looks and reads like real paper, even in bright sunlight.