If you haven't picked up your cell phone headset or speakerphone for the car, you only have a few more hours or you will risk a ticket and fine in California. Starting July 1, 2008, all automotive users of cell phone will be required to use some form of hands-free device when calling from their vehicles.
I have been a big fan of cell phone headsets, even back when they were typically wired to the phone. Hands-free cell headsets allow the easy use of voice dialing and great services like Jott.
If you don't have a headset yet, here is a link to the one I use, an Aliph Jawbone. There is also a new, 2nd generation Jawbone (available at their web site) which is much smaller. It's built in noise reduction features are great. You can see a demo on their site. (Video demo)
Link: More Bluetooth Headsets from Amazon.com