Audible is having their
Semi-Annual Sale with thousands of books for $9.95 or less. (not sure if it's members only)
Ends April 26th @ 11:59 ET (US)
The link only shows "Highlights by Category" and includes only 344 books. I didn't see a way to view everything that's on sale so if anyone finds a better link please post it.
Remember, if the book has a regular price of $14.95 or more then it qualifies towards the Buy 4, get $10 listener rewards promo too (through April 30th).