Yes, a cassette adapter. 🙄
At least where I live/work, I can't get a consistently clean signal. I got tired of chasing the FM band around the Baltimore beltway, returned my iTrip, and got a cheap cassette adapter. A little hiss, but if you keep the iPod volume about 35-40% then use the car stereo controls to adjust, it's not so bad.
I know two other people who bought, then returned the iTrip for the same reasons, and no one who kept it.
Still, I'm thinking my birthday gift to me this year is getting a hardwire install in my truck for the iPod.