1. Griffin DirectDeck HandsFree ($24.99)
Never satisfied with the audio quality of FM transmitters, I've relied on cassette adapters for years. Griffin's DirectDeck HandsFree adds a microphone atop the auxiliary plug, making for a welcome update to the old standard. When combined with a simple dashboard mount, this makes for an easy, inexpensive setup.
2. Griffin AirCurve Window Mount ($39.99)
Griffin's AirCurve iPhone docks have been around for a few years now. Their unique construction amplifies your phone's volume acoustically, so no cables or power are required. The AirCurve Window Mount is the company's latest addition to the line, bringing acoustic iPhone amplification to your car. Your phone's battery life will thank you for this Bluetooth-free wireless solution.
3. iHome iDM11 ($69.99)
iHome has been making iPod accessories for years, perhaps most famously their line of speaker docks with integrated alarm clocks. While they've always had decent audio quality and plenty of functionality, they've never been the sexiest gadgets. Enter the newly-released iDM11, which may be the most attractive piece of hardware the company has ever produced. The diminutive Bluetooth speaker plays music in mono, and serves as a speakerphone for calls as well.
4. Jawbone JAMBOX ($199.99)
Jawbone's JAMBOX is a truly impressive speaker. The little brick packs a tremendous punch, easily filling a room with surprisingly crisp sound (If you'd like to hear one in person, they're often on display at Apple Stores). Like the iHome speaker above, the JAMBOX features a built in microphone for speakerphone use. This is a solid and stylish unit.
In the end, the first two products are excellent low-cost solutions, but are limited to use in the car. On the other hand, the Bluetooth speakers are portable and self-contained, so you can also enjoy them at home, at work, or just about anywhere. Still, neither iHome or Jawbone include a car-mounting system, so a bit of DIY magic may be required to keep these speakers safe and sound as you drive along.