As kerzain pointed out here we could really use a Kindle ebook bargain thread.
I just got my Kindle a few days ago. I'm clueless as to how to find bargains on Amazon's site. I've been buying ebooks for some time other places though. Quite a big fan of Webscription. Their content is a few specific genres of Fantasy and Military Sci-Fi. What I really like is the "Webscription" itself. 5-6 eBooks available for $15 per month. Usually 1-2 newer titles and a selection of their older titles. Their eBooks are DRM-free, multiformat, and available as MOBI files. You can email these to @free.kindle.com.