In case anyone missed it, effective January 1, 2008 there are new FAA restrictions on lithium batteries (including lithium-ion batteries) in both carry-on and checked baggage on US flights.
These are the newer type of rechargable batteries used in handhelds, as well as laptop computers, camcorders, cell phones, etc.
The rules are clear as mud. There are distinctions made between batteries 'installed' in a device and 'spare' batteries.
Most consumer sized batteries that are installed in devices will pass if in your carry-on baggage. However, if you are carrying lots of gear, and lots of batteries, you might run up to restrictions on the total grams of 'equivalent lithium content', or the amount of carry-on items permitted!
I would hate to see someone lose a $60+ battery because they missed this.
More info is available on the official FAA website:http://safetravel.dot.gov/whats_new_batteries.html