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
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