your 6800 should have come with a 'Y' shaped adapter. it plugs into the usb port on the bottom of your phone. then it has 2 leads: one for power and one for a 2.5mm headphone jack.
all you need is a 2.5mm to 3.5mm adapter. radio shack has them.
from that you will have the same output as any MP3 player so you can usecheap fm transmitter or tape deck adaptor (if u have a tapedeck)
something like this will work:
http://www.radioshack.com/product/in...entPage=family
i know u can something cheaper that does the same thing.