The duaLink sync and charge splitter cable for iPhone and iPod lets you sync and charge two devices from a single USB port.
Read the duaLink Press Release for more details about this fantastic cable.
Note: duaLink is designed for computers and does not work with wall or car chargers. If you're looking to charge multiple devices from a wall or car outlet see the dualCharge or dualCarCharge.
Note: duaLink will sync an iPad with iTunes when connected to a computer, but the iPad will not charge. The iPad requires all the juice output by the USB port. The duaLink splits the charge, giving the iPad less than necessary.