The problem with using a standard FireWire cable (for 1G and 2G iPods) or the iPod's dock connector cable (for 3G and later iPods and the iPod mini) to connect your iPod to your computer is that iTunes wants to launch to sync your music and, if you've enabled the option, your iPod wants to mount as a hard drive. Even worse, if you plug your iPod into a computer other than the one it's linked to, you get a message asking if you want to instead link it to the "new" computer -- accidentally click the wrong button and your music disappears off your iPod.
Sometimes you just want to charge your iPod, whether it's at home on your own computer or on the road with a friend's. SiK provides a handy solution with their power-only FireWire cable, the HotWire. The HotWire looks just like a standard 6-pin to 6-pin FireWire cable but it carries only power -- no data -- making it safe to connect your iPod to any FireWire-equipped computer. It's only drawback is that to use it with dock-connector iPods, you need a FireWire-to-dock connector adapter such as SendStation's PocketDock or SiK's own din or din ram.
In the "tools we use" department, I always have a HotWire and a SendStation PocketDock in my bag -- I'm able to charge my iPod with any 6-pin FireWire-equipped computer (such as my PowerBook, which doesn't contain my iTunes Library) without having to worry about syncing or Library issues.
Power-only FireWire cable for charging your iPod.