What transmitter do you have now and hate?
I just got myself the new iTrip with car charger and it's so much better than my old iTrip was.
here's the one i have now: http://www.griffintechnology.com/products/itripauto/
plugs into the bottom of the ipod and into your car charger. the fm transmitter is in the middle, and it's powered by the car which is very nice. easy to switch stations with +/- buttons right on the transmitter. clarity is 100% better than the old itrip.