Or... you could just get a battery grip.
Link. That's what I'm doing for my trip to Costa Rica.
I'd still bring a backup system of some sort -- with VR lenses, the occasional onboard flash use, and the quantity of pictures I am capable of taking in two weeks, I am definitely capable of killing more than two batteries on a two week vacation.
I'd hate to get caught part way through a trip and no longer be able to use my D80! I know the battery grip can use AA's, but I would consider that emergency last resort (by virtue of the cost of batteries in places I've traveled to).
After relying on the power bricks to charge my D80, camcorder, and MacBook on several trips now, I'm pretty comfortable with the concept; the plug adapter is inexpensive and takes almost no space in a suitcase -- I couldn't see traveling without it, even if I didn't expect to use it.