As far as I know there is no way to “control” a USB Hub. You can deactivate devices in the OS, but that just makes the OS ignore them – it does not turn off power to the device. There is no direct way to control 5V power to USB devices through software on most machines.

The absolute cheapest way to do this would be to hack a Serial port on the computer (therefore bypassing USB control through the Arduino) and hook up a transistor to switch the lights on and off, but you’d still need to make a 5V supply and such – not exactly an elegant solution. The Arduino makes this project easier and neater because it incorporates a 5V supply and a USB connection to transmit data to/from the computer.

Right now I’m designing a really basic board for the lights using a transistor instead of the relays to keep cost down. The downside is that the transistor results in a voltage drop – about .2V. That’s fine for the lights (they still run, just not quite as fast), but it shouldn’t be used with any other USB devices. I’ll post more about it soon once I have the preliminary design finalized.

As far as cost, here’s a breakdown:
- Arduino (or similar clone): $15-30
- Darlington Array chip (ULN2803): $1-2

Optional (if you don’t have these)
- USB A-B cable
- 9-12V Wall Wart: $10
- Small bit of protoboard to make it permanent: $1-2
-Altoids tin: $1-2

Of course, you’ll have to supply the woot-off lights, which I think are $10-15 when Woot has them (or anything else that runs off 5V/USB power). You could also replace the Darlington array with a standard small-signal transistor, but I didn’t have any lying around.