Motion
Motion is an open source "software motion detector". http://www.lavrsen.dk/twiki/bin/view/Motion/WebHome
It's a command line program, designed to run optionally as a "daemon". It uses Video4Linux for camera input (e.g. webcams). It includes scripting possibilities.
By default, motion, puts some interesting files in the following places:
/etc/motion/motion.conf /var/lib/motion/snapshots /usr/share/doc/motion/examples
Following the "tuning" instructions: http://www.lavrsen.dk/twiki/bin/view/Motion/TuningMotion
To start I opened a terminal, made a folder to work in (in my system /home/murtaugh/Documents/motion), and cd'd into this folder. The I made a copy of the default conf file to make changes to. When you start motion, it will first look for a file named "motion.conf" in the current directory. You can also start it with the "-c" option to specify a custom configuration file (useful if you have different kinds of setups you want to test).