Non DRM Mobipocket format is already supported on the Kindle - just drag and drop.
Kindles can read a variety of non-proprietary, non-DRM'ed formats. They read TXT, HTML, JPEG, and non-DRM Mobi files directly.
Plenty of free e-books in Mobipocket format show up fine on Kindle.
A cheap casioppeia allows me to read ebooks around 2001.
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.