I've got a kelty noah's tarp I use for backpacking. Works pretty well, not too expensive, lightweight.
Also, I bought a cheap 10" x 10" (dimensions approximate) throw pillow from a walmart type store for $5. It gets stuffed into my stuff sack with my sleeping bag, or sometimes just stuffed in a rear pannier. The pillow is quite luxurious for camping. The idea came from another BF member.