I once came across an encyclopedia of signs and symbols (or a title similar to that) in a college library. It was very interesting, and broke them down by general characteristic (i.e. all the hammer type symbols were in one section, all the moon type in another). Or, you might want to see if you can find books on the Masonic tennants. I've been seeing more and more of them pop up in "New-Age" style book catalogs and such.