I use 2 methods, depending on the machine: FTP or USB floppy drive.
FTP works great. That's how I'm sharing files between my PM 5200 with 8.6 and my Mac Pro with 10.8. Get an old copy of Fetch for the old machine.
If you don't have Ethernet, then you can do what I do with my CC. I picked up a cheap $10 USB floppy drive. Since the CC reads 1.44s, it's not a problem sneaker netting files from my Mac Mini (running 10.5 for classic HFS) to the CC on 1.44 floppies.
FTP works great. That's how I'm sharing files between my PM 5200 with 8.6 and my Mac Pro with 10.8. Get an old copy of Fetch for the old machine.
If you don't have Ethernet, then you can do what I do with my CC. I picked up a cheap $10 USB floppy drive. Since the CC reads 1.44s, it's not a problem sneaker netting files from my Mac Mini (running 10.5 for classic HFS) to the CC on 1.44 floppies.