My best guess is that there's isn't anything that reads PC formatted disks on the Mac, simply because the Mac OS is supposed to. Hopefully I am wrong though.
Do the computers that need to access this drive on a network together? If the Macs have 10.2 Jaguar installed, you could transfer the files through the network. It won't be as fast if you have fast Ethernet (100 Mb), but if it's 10 Mb, it's gonna be a dog.
Have you thought about formatting the drive as HFS+ and then using Macdrive or an equivalent on the PCs?