My friend Mark is flying off to Taiwan in a few days, and in honor of his 24+ hour flight I should I'd mention this find.
The Inflight USB Power Unit plugs into the audio jack of your seat and outputs power to a USB plug allowing you to charge your iPod, phone, PDA or whatever. From their site:
Plug compatible with any standard USB charging cable. The Inflight USB Power unit plugs into the passenger seat audio jack and outputs regulated power to the attached USB charging cable/connector.
I can't speculate on how well this would work, or how the airlines would feel about it. It's kind of a one-trick pony for $35 but might come in handy.