I should have mentioned this in the earlier tip about free and public domain books.
Many free eBook sites allow you to download their books directly to your Kindle. This saves time and sometimes money. Just go to the mobile version of the web site. The following websites are Kindle friendly:
Advanced Tips: Some magazine and periodical web sites will also allow you to download old issues and articles to your Kindle. Unfortunately, most of these sites will use text or other files.