Watts Up Electricity Consumption Tracker

Like the popular Kill-a-Watt, the Watts-Up electricity monitor sits between the device whose energy you would like to track and a wall outlet. Both devices present you with a handy display of power comsumption, but the Watts-Up Pro (not the standard) has a USB interface, which allows you to download the stored data onto your PC for further analysis. The data can also be exported to Word or Excel. Conveniently, the Watts-Up displays the cost, in dollars and cents, on the unit's LCD screen.

See also:

Watts-Up and Kill-a-Watt at Amazon.com
The Gadgeteer's review of the Kill-a-Watt