Directly from the Compatibility section of the documentation for MAC OS X 10.4:
Removable media and devices
A variety of other removable media and devices can be used to exchange files between
Mac and Windows systems, including Iomega Zip disks, USB disk-on-key devices, and
removable (external) FireWire and USB hard drives. For best compatibility, these devices
should be formatted using the FAT32 file system, which is supported by both Mac OS X
and Windows. Mac OS X also supports the ability to read files from devices that use the
NTFS file system format.