On the DCS faculty and research Linux machines running Fedora Core 2, they can be accessed as one of /mnt/removable/usba, /mnt/removable/usbb, /mnt/removable/usba1 or /mnt/removable/usbb1. The actual name varies depending on the machine, so you will have to experiment.
These drives don't show up on a df when plugged in unless they're actually in use. Also, "ls /mnt/removable" will not show anything there. You must type out the complete name of the device.
Note: Since these devices are formated with windows filesystems, files and directories on them are world-readable and -writable. It is therefore inadvisable to leave one plugged in if you have anything valuable or private on it. The ephemeral nature of their mounts is an advantage in this respect.