For Installing or developing Drivers.

Installing Drivers:

• Linux Device Drivers Demystified tutorial @ LinuxPlanet
  list of drivers
  Linux-kernel mailing list FAQ - see section 2 on device drivers
  www.linhardware.com
  Linux support for some Winmodems
  PCMCIA
  USB (includes driver development)
  

Developing drivers:

• Linux Loadable Kernel Module HOWTO (as 1 large html file)
  Linux Kernel Module Programming Guide
  Linux Device Drivers 2rd for 2.4.x (whole book online)
  Linux Device Drivers 3rd for 2.6.x (whole book online)
  Linux-Treiber entwickeln for 2.6.x (German, whole book online)
  Linux Devfs (Device File System) FAQ
  Misc Character Drivers
  I/O port programming mini-HOWTO
  linuxassembly.org
  Porting device drivers to the 2.5 kernel
  Writing Portable Device Drivers
  WritingPortableDrivers
  User Level Drivers
  

Links:

• Hardware Support
  Drivers
  

MindShare, Inc has a nice series of books on various bus protocols, including PCI, USB, PCMCIA and Cardbus (from http://www.handhelds.org/pipermail/ipaq/2000-November/002223.html).

KernelCodeRepository : users kernel code