DRM refers to the fact that you can't view Amazon Kindle books on other devices (including your computer), or on other Kindles - i.e. no sharing, the purpose of DRM.
There are converters available from Amazon and/or Mobi for pdf and doc files.
As glued to the net as we all are, there's vast quantities of content that is not available online.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
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.