Installing SANE

If you've got Red Hat Linux, then you've got a recent version of SANE in 
RPM on the distribution media. Mandrake comes with SANE, and Ximian 
installs it as well.
Installation from source is the usual ./configure;make;make install

Depending on your scanner type, your kernel will need generic SCSI support 
(sg) and/or USB support (usb-ohci/usb-uhci). I would personally recommend 
using the 2.4 kernel, especially if using USB.

SCSI: 
Make sure the adaptor driver is loaded, then the SCSI adaptor and the scanner should be visible at /proc/scsi/scsi
If the scanner is supported by SANE, scanimage -L will list it.
USB:
For USB scanners, you'll probably need to modprobe scanner.o in addition to usb-uhci or usb-ohci.
Again, scanimage -L should list your scanner, but it depends on the device.