CC Validation

I'm making a shopping cart script and i'm having trouble grasping the whole credit card validation and storage thing.

I've got the cart running so smooth (i could sell it and make a ton, but it will be free i think). Anyway I can't find a good way (and secure way) to validate the credit cards and store them using SSL or some other sort of encryption ecomerce sites use.

can someone point me to a good web site that has information on dealing with this?

thanks