I have successfully connected both of my Toshiba 2.5' HD (one 20G 4800rpm, the other 40G 5400 rpm). Both of them need to have external battery supply. My usb cable for the hd housing came with two usb male connect at one end (one for data&power, the other for extra power). I guess z usb host end can't supply enough power for the 2.5' hd, kinda like an unpowered usb hub and things in that class. The new 1.8' hd can suck power directly from the z as mentioned in the other thread. Rio carbon connects no problem. So I'd guess items with their own power like rio karmar, Zen Xtra, iPod would probably work with Z too. But don't take my words for sure.
dmesg spits things like scsi simulates usb mass storage. then I mounted /dev/sda1 to /mnt/usbhd. that's it.