Margaret,
I guess The Memory Book by Harry Lorayne and Jerry Lucas was one of the better books. His other books rehash much of the information he has given before, but I probably base my opinion on the order I read them, The Memory Book being the first. The Memory Book also does cover pretty much everything in the other books, while the others may be more specific. He also has some tapes, but I didn't find these worth as much as a book, plus they are more expensive. Dr. Kenneth Higbee's book Your Memory: How it Works & How to Improve It also has the same information in techniques but it is more scientific. Think of Harry Lorayne as a How to guide while Higbee is more of a scientific/explanatory guide.
Be warned though, in a way these techniques are somewhat the opposite of PRing - the stress is on being 'originally aware' of information, no unconscious preprocessing here. Though (if PRing works) I could see how the systems could complement each other.
Anyway, I found the memory book, and the trachtenberg system to be the only substantially useful techniques for me. I don't know if the trachtenberg would be useful to anyone else who already knows arithmetic though, it's hard for most people to get out of their habits and into new ones.
