Haven't built it yet, but I thought I'd pass it on.

I'm not so keen on PDAs, myself, and I cac remember music almost as well as an iPod without the need for recharging. I figured some here, though, might find it nifty. <img src="/images/graemlins/smile.gif" alt="" /> Basic circuits was a long time ago for me, so someone shout out if I get this wrong. I probably will; I should check my external memory (books).

Input on the reg goes to the positive terminal, output to the device, ground to the negative on the battery. I'd build it, and then hit it with a meter to be sure, though. As I said, it's been a while for me; even if it wasn't, test everything first. These bits are cheap.

Silly me- twice I forgot to put this in:
http://misc.hackaday.com/entry/1234000520028239/
They also have this guy, which is a bit simplier. But maybe a bit too simple for my taste. It NEEDS a switch, or just take the battery off when not in use, becuase it will make a little heat for a while, then the battery will be dead.