Check out the book, Taking Charge of Your Fertility. Also, The Beautiful Cervix Project
really helped me understand not only CM, but CP as well. Good luck!
Again, jschwind beat me to it. I was actually a little grossed out by the Beautiful Cervix Project at first, but it really helped me understand my cervix a lot better.
Yeah, don't go to the 'abnormal cervix' parts of the project unless you want to not be able to eat for a few days...but I agree, it's a little weird at first looking at all those cervixes, but it really does help to know what's down there. I had no idea at all, and always wondered how docs could tell how dilated it was, but now I know!