I try to limit my promoting of things here but in the interest of cheap gamers everywhere I felt like I should mention this one. It's Savage September on DriveThruRPG and they have some nice setting books for Savage Worlds on sale for five bucks. This includes Weird War II and Interface Zero.
No I don't know any of them personally or work for them or get free stuff from them or anything else. I just like Savage Worlds and I also like good deals, so there you go.