I saw someone post the other day on a good simple CSS tutorial...i believe it was tidbits.com i started my adventure with lissaexplains.com...... i thought it would be good to point out a good progression of tutorials
CSS tutorials Well this is just a selection of css code for menu's http://css.maxdesign.com.au/listamatic/index.htm Great site to get your menu started then tweek to your taste
The official CSS specification is CSS from beginning to end. This is your encyclopedia of properties. HTML Dog has good tutorials on how to use those properties on your pages. Some of the informatioin presented here is not reliable.
I always direct people to the two books by Dan Cederholm. His site is simplebits.com. Also, look at alistapart.com. You can find a lot of in depth how tos there as well.