I've used a couple of cheap (ish) ones from gomadic.com to charge my Edge 305.
Ideally I want one that will take double AA's, and then that will alleviate the problem of having to recharge a rechargeable on long wild rides in the middle of nowhere and living rough with just the odd shop around.
If you mean a power brick that has USB connectors amongst others to keep you going on the move, then I've heard nothing but good things about the Pebble.