Green Ronin is liquidating their D20 stock through distributors, $2.00 a book.
is one online e-tailer that is honoring the sale. $2.00 paperbound, $10 hardcover (I think)

Favorites from past experience -
Skull & Bones - Yarr!
Medieval Players Guide - Medieval England setting and D20 rules.
Advanced Bestiary - Templates, lots of them. Best is Jotunblood Giant.
Freeport Trilogy - Yarr!
Testament - Roleplaying game based on a single book. The first chaper is Genesis....
Skull & Bones - Yarr! (At $2.00 it is worth mentioning twice....)
Thieves World - Assorted prices of the Robert Asprin Thieve's World setting.

The Auld Grump, did I mention Yarr!?

Yarr!

Unfortunately my 'Yarrr!' turned to 'Arrrgh!' when I discovered there is no PDF option. $2 for Freeport Trilogy, $9 for shipping, and it probably wont be here until after Xmas.
Anyone know if the PDF is available somewhere?

I run also when I saw your post...but sa cheap as 4 books for 11$ is the problem is the 39$ shipping cost to Spain (all an all it makes a 10$ per book...but is not the same as 2$) - Lately the $ is down for us...but the shipping cost have made difficult to buy...They have gone tooo high lately ...