I don't have a Kindle, but they are awesome. My friend has one.
I found this info -
Kindle makes it easy to take your personal documents with you, eliminating the need to print. Each Kindle has a unique and customizable e-mail address. You can set your unique email address on your Manage Your Kindle page. This allows you and your approved contacts to e-mail Word, PDF documents, and pictures wirelessly to your Kindle for a small per document delivery fee--see details. Kindle supports wireless delivery of unprotected Microsoft Word, PDF, HTML, TXT, RTF, JPEG, GIF, PNG, BMP, PRC and MOBI files.