Originally Posted by Eragon
Good questions. I personally use a Macally JBox. It is a lithium ion rechargeable battery that connects to the iPhone via the USB to dock connector. I use it when I am on travel and need to recharge my iPhone. Comes quite in handy for watching videos on air planes.
Another option is the juice pack by Mophie.com. I personally like the juice pack as it is a single unit which attaches via its own dock connector. It only recently was released. It too is a lithium-ion rechargeable battery.
With either battery, you are guaranteed to get lots of video time (3-4 times the native iPhone video playing time).
would you post some links they sound good