Many mp3 players recharge through a USB connection. What do you do if you go on holiday without your computer?
On a recent trip, three of us had mp3 players that would need recharging while away. The last thing we wanted was non-functional music when sitting on the beach, or on the airplane.
The solution: a USB hub. You can pick up a USB hub quite cheaply. Get one that comes with an AC adapater, so that it provides its own power. This will recharge your battery. Be sure the connectors are arranged such that you can connect all the mp3 players at the same time. Test it at the shop if you can to be sure that it really does charge your mp3 player.
Hope this helps!