Canonical source of Linux + hotplug info: Linux-hotplug at sourceforge
Software from kernel.org: /pub/linux/utils/kernel/hotplug (includes rather strange udev FAQ!)
"Historical" note: Richard Gooch on devfs
Fine-tuning udev: Writing udev rules
Software from freedesktop.org: freedesktop.org - Software (for dbus, hal and all that)
One entry-point into a very useful mailing list: udev, hal, and usb mass storage
Useful notes from another LUG: WLUG-Wiki - Hot Plug Notes
Various folks' experiences and advice:
Debian GNU/Linux and the Canon PowerShot A40
Usb-mount - a user interface to USB-storage for Linux 2.4.x and 2.6.x