Linux can access most USB devices as far as I know. Some, like some cameras for
instance, uses own protocols and requires special programs beside the normal
USB access. USB acess for devices, e.g USB mass-storage is built as kernel
modules. If you got the opportunity to choose; go for devices that uses the USB
mass-storage standard. Harddisks, "memory-keys" and some cameras (I got a Nikon
coolpics2100) uses it.
Regards, L Ekman