If you don't have it already, do yourself a favor and print this CSS3 cheat sheet. It has a complete listing of all the properties, selectors types and allowed values in the current CSS3 specification from the W3C. Each property is provided in a section matching it with the section (module) that it is most actively associated within the W3C specification. Next to each property is a listing of the values that that property takes (normal text shows named values it accepts and italics shows value types it will accept).A very handy tool to have around — download link is below.
Link: CSS3 Cheat Sheet