L.L.
For part of my pregnancy I used a pregnancy pillow (made by Boppy) but that was specifically because I was having alot of hip pain from laying on my sides so much.
Also, I just bought a 4" Memory Foam Topper from Overstock.com that we put on top of our pillow top mattress. It just felt like the pillow top had lost it's softness and we couldn't afford a new mattress. The topper we bought only cost $80 for a full size. It has made a world of a difference.