This guide will help you retrieve the qc-usb drivers for your Quickcam.
Downloading and installing
This module is in AUR. As I write, the dependency kernel26-headers has been left out of the PKGBUILD, so you'll need to install it manually.
Finding the module
The module is called c-qcam. Load it with modprobe or add it to MODULES in /etc/rc.conf. Udev should autoload it on reboot, though.
NOTE: If you have a Logitech Quickcam Messenger webcam, you need the qc-usb-messenger package, also in [community].