Any reasonably recent distro (say not older than 3-4 years) would work with an external USB hard drive. Usually when you run in text mode and plug-in the HDD you'll see a message about a new device discovered. If that doesn't happen you either have to manually load-up some modules or recompile your kernel.
Usually external devices are registered as SCSI-ones (/dev/sdXY). If running devfs or udev you'll have a device node automagically created; otherwise you can use MAKEDEV. From then on, it depends on partitioning type. If you're talking about PS2 HDD you can try hdl_dump or pfsshell. If it is FAT-formatted just mount it and use regular commands to copy your bytes.
"Only those who try will become." -- Kimahri Ronso