I thought this might be of interest to some of you people, so here goes.
I have a soshine two way USB charger and 4 900mAh batteries for it, (linky 1, linky2), and also waiting for a CA-100 (linky). These three devices put together should technically provide normal charging for the N800/N810. The USB battery pack can output 1000mAh, the AC charger for the nokias use 890, and the batteries are 900mAh so in my screwed head that comes out to normal charge for an hour, although in rteality prob less due to battery inefficiency and energy loss. Either way, at a total of 21 bucks or so shipped worldwide, I'd imagine it would be useful for a lot of people. I have yet to test this though, but the charger works for my cell phone, and both my mp3 players (piccy)