Macs prior to September 2003 with Firewire ports are much better equipped to handle the older Firewire compatible iPods than the new USB based iPods.
The USB 1.x ports on pre-September 2003 Macs, while capable of connecting to newer iPods, will only connect at 12 Mbps compared to Firewire's 400 Mbps.
Additionally, many won't power the iPod when connected.
Some third party addon cards are available, but make sure that any you get has the ability to power the iPod, as not all do.
The following iPods are Firewire compatible:
6 pin firewire cable compatible only:
1. iPod first generation (scroll wheel)
Firewire dock cable compatible: