Apart from the floppy disk drive, I have only tried one other USB device: a Kodak DC 280 Digital Camera.
Although this is recognised as a device on the bus, if you try to mount it using (for example)
$ mount -t vfat /dev/sda1 /mnt/camera
you get a message telling you "/dev/sda1 is not a valid block device".
I believe I may have used the wrong syntax for mounting the mass storage device... The camera does, however, work perfectly with gphoto. Goto
Configure> Select Port/Camera Model and select the camera from the drop-down
menu. Then under port, select "other" and enter
/dev/usb/dc2xx0
To avoid problems with non-root user permissions, change them as follows:
$ chmod 666 /dev/usb/dc2xx0
Note: I was able to mount the Camera Compact Flash chip from a Compact Flash PCMCIA adapter at a later date...
The adapter was assigned /dev/hde1 when it was plugged into the PC card slot, and the relevant mount command was:
mount -t auto -s -r /dev/hde1 /mnt/flashdisk
You will have to create a directory in /mnt named "flashdisk" or similar. Maybe the same type of mount command (for /dev/sda1) would work with the camera, but I have left the interface leads in Scotland and cannot check right now.
Details of the support status of other USB devices under Linux can be found at:
http://www.qbik.ch/usb/devices/