Do you have an input socket on your car stereo? looks like a headphone socket. Pluga 3.5mm jack-3.5mm jack from that input socket to your BB's headphone socket. Then on your stereo selector (Radio. CD...) his Aux or input and away you goooo!
I have a USB input on my JVC, wish I could just plug directly into my BB. I however have about 8GB of MicroSD, SD & Memory Sticks that I alternate. As flash memory continues to drop in price, I don't see how the CD industry has even made it this far.