Hi Amber,
Intestesting you should ask this. I was looking for one earlier today and was amazed at the poor ratings on ALL of the ones I found. Granted they are for the iPod and connect to the dock port, which is not what you want.
So, I decided to try the one I bought years ago to work with my iPaq where I listened to audio books while on trips. I wanted to replace it for 3 reasons: 1. It runs on AAA batteries which last about 20 hours, 2. The device plugs into the headphone jack, 3. It only has 4 channel options in the 88.x Mhz range.
Many complained that their devices were cheaply made and broke within a week. Others said that their units did not have enough power if the car antenna was in the rear window and there was a good deal of static (EMI/RFI) along with the music very noticable when no music was playing.
Well, I connected my iRock to my iPod and was very pleased with the results. When I turn the device on, the channel goes totally quiet until the music or audio starts. The only thing I noticed that was a bit off was that the bass was over stated. But, I can adjust the setting on the radio to compensate.
I found one here:
iRock FM Transmitter You will note that the price is right!
Good luck!