Parallel Port: A special case of SANE-ity.

Parallel port scanners are a different kettle of fish. In order to use one, you'll need to enable ppscsi support in your kernel, which is not present by default.

The ppscsi source can be obtained from http://www.torque.net/parport/ppscsi.html
Apply the patch, recompile the kernel (I did this using 2.4.3).
Make sure to insmod scsi_mod, sg, parport, parport_pc, ppscsi, and the specific ppscsi module that matches the scanner you own (there is a list on the ppscsi website)
After this, scanimage -L should list your scanner.
If you do this under X don't be surprised if your system freezes for the duration of the scan. That's the downside of parallel port devices.