This may not be for everyone, but Amazon has started to price-match many of the books listed in the
Borders.Com $5.00 eBooks Sale (around 200 books are $5 on Borders now).
Here's a search link for Amazon that should update with new books that are discounted to $5.00.
Some are pretty great deals, like Kazuo Ishiguro, John Grisham, Max Brooks, etc books for $5.00 only.