I picked this 120 Watt power inverter up at Frys for $19.99. It is smaller than the APC inverter mentioned earlier in this thread, and much less expensive. It has connections for both car and Empower, and a USB port to charge things that can do that. It has a nice felt carrying case that holds everything.

I used it on a flight from ORD-NRT-BKK with little issues. The only problem I had was when I placed it so that the fan was blowing into a blanket and the device overheated. Once I moved it into the open, it worked great. I did not have the opportunity to try to power a laptop and charge a USB device simultaneously, but the instructions say this is possible. It did power my Dell Inspiron 9300 (a beast!) with no problems.

I'm still going to get the Tumi universal notebook power supply b/c my Dell power supply is going to break soon, but I thought others might be interested in this little gadget.