The API used for accessing scanners under linux is called SANE.
USB scanners have their driver in UserSpace (at least in 2.6 linux kernels), and this is provided by the sane backend using libusb. For this to work, you will need the virtual 'usbfs' filesystem mounted on /proc/bus/usb (although your distribution should do this automatically).
You can control which scanner drivers are loaded in sane's dll.conf config file (located in /etc/sane.d/dll.conf in Debian Sarge.)
Sane should also come with appropriate HotPlug scripts. Make sure you have appropriate permissions to access the device - in Debian, the USB device file will be read/writable by people in the "scanner" group, so add any users to that group (and log out and back in for changes to your current user to take effect).
If you are looking for a hardware flatbed scanner that works under linux, Epson-branded Scanners seem to be well supported. Hewlett Packard scanners and printer/scanners also seem to be well supported. HP have supported hpoj and hpijs drivers which are included in some distros.
See also HardwareEpsonPerfection1660 for hints about that photo scanner.
Canon have a USB2 scanner in their "!CanoScan?" series called the "LiDE 20" which worked fine with the SANE scanner libraries in linux. (Apparently the LiDE 30 works as well.) It is based on the same chip as many Plustek-brand scanners, so make sure "plustek" is loaded in sane's dll.conf file. This scanner is also completely powered through the USB cable, so make sure it is plugged directly into a powered hub and not daisy-chained through another device or unpowered hub.
Part of CategoryHardware
4 pages link to ScannerNotes:
