VIGO Digital Wireless Automobile FM Transmitter with LCD Display - White
Full range of FM frequencies means I can find any empty frequency in my location to use without being limited by presets. I have on occasion set it to the same frequency as a strong station and still been able to hear my MP3 just fine. Batteries tend to die after about 3 hours of continuous use which stinks for long commutes.  I use solve that issue by using rechargeable batteries on the go and a universal AC adapter at home. Sound quality is not bad.