Every iPod/iPhone cable should should be compatible for charging other iPods/iPhones, except the first gen iPod which used standard firewire instead of the iPod connector we're all so fond of now.
Not every one will work for playing music through or transferring data (ex: firewire/30pin cables on the newer iPod models, some iPod docks/connectors with iPhone)
My first iPod had a cable with a firewire connector. My second iPod and iPhone have a USD connector. I haven't had any problems using either cable on any of these devices.
incorrect, the first and possibly second generation ipods (im sure about the first, not so much the second) had a firewire cable, and not the common 30 pin dock connector we are used to seeing