Five states have passed laws making it illegal to hold a cell phone while talking on it in a car. The California law takes effect July 1, 2008 and will cost drivers $20 for the first offense.
Personally I haven't found an ideal alternative to holding my phone up to my ear. Aliph's Jawbone has the best repution for sound quality and noise reduction but there are universal complaints about the fit on your ear. At CES this year Jawbone ran a promotion that offered a free Jawbone with a trade-in of any bluetooth phone. I took them up on it and immediately discovered what other users found - it just didn't feel secure comfortable on my ear. On the airport tram ride to my gate I happened to overhear someone telling a new Jawbone owner that it was very common for owners to replace the standard earpiece with a gel ear bud from Jabra. You can get six of them for around $6.00 on Hello Direct or OEM versions on ebay. I have to say it did greatly improve the fit. We'll see how it goes.