I've mentioned getting Kindle books from other sources, it's easy and free/cheap.
Bundle sales:
These folks do software bundles but have done several ebook bundles. Multiple books for $4 to $____ in price. Usually bundles have a theme: young adult, sci-fi, romance, etc. A lot of times they contain a first book (or two) in a series, that's why it's cheap to get you hooked.
http://bundleoftheweek.com
http://www.ebookbundles.com
http://storybundle.com
http://blog.humblebundle.com/post/33...e-ebook-bundle
(I like humble bundle but they don't always have book sales so it's confusing to send people there).
I've used
http://storybundle.com and
http://humblebundle.com and I think both were able to send the books directly to my Kindle (I had to approve their address once). I think most of these bundle sites have the books in both EPUB or MOBI so you can put on most devices (iBooks, Kindle, Nook, Kobo).
Sharing book sites.
Many (most?) Amazon purchased Kindle books can be lent once, but who do you borrow from. I've had the most success with Lendle
http://lendle.me
I've also used
http://ebookfling.com
http://booklending.com
ou usually get a few borrows but then you need to lend some to get some credit (a few sites Ylet you pay for credits), I've got 40 books credit on Lendle so it's easy to do. *The site matches you and but an actual lend is handled by Amazon. *No one can keep your book for more than 3 weeks, it's automatically returned by Amazon. *They have a week to accept a book loan and 2 weeks to return it. (If you're going to sign up for Lendle.me to borrow books, please use my referral code TTXLDIO1 It gets me a few extra borrows. Thank you.)
Free classic books (Oz, HG Wells, Little Women, etc.) and other CURRENT public domain books.
http://www.gutenberg.org/wiki/Free_Kindle_Books
They even have a really easy when to browse their site and download books directly (but this does not sync with other devices under that option, but if you're a one Kindle person this is perfect).
Directly from authors:
http://ebooksdirect.dianeduane.com/collections/all
A favorite author who has been updating / rewiring portions of a series of books she started 30 years ago (So You Want to be a Wizard - Young Wizards series) but were a little stale and out of date (people were using Apple II and there were no cell phones). She updated the books, fixed typos, fixed minor inconstancies and restarted the series to take place in 2008. IMPORTANT: These updated books are NOT available anywhere else so buying from other sites is sometimes the only option. She has all her other books too (and a few other authors) and most single books come with EPUB
and MOBI versions. She also does sales a lot too, so sign up for the mailing list. This is just one example, I'm sure many authors do this too.
Your PUBLIC library! Many consortiums and libraries have tapped into Kindles catalog for lending. Check with your local library. You do it from home and when you find a book you borrow it (just like purchasing it) and you get the books for 2 weeks. Mine even lets me put books on hold
Kobo: I think if you buy from the Kobo web site, the books are unprotected so you can install on some devices but Kindle is MOBI so you'd need to convert it with something like Calibre first, this is inconvenient but once you've learned to use it, it's pretty great.
Calibre also has 1,500 news feeds (CNN, Wired, Cosmo, Field and Stream, New York Times and other newspapers from around the world) you can get on your device for free (Kindles from the Touch and newer [late 2011] need to hook up via USB for the news feeds to look nice and proper), older kindles [Kindle Keyboard and earlier] can have Calibre e-mail them to the device directly. It's a little tricky to figure out, but then it's automatic!
http://calibre-ebook.com/
Gary