IMLocation does useful stuff for you, based on where your laptop physically is, and what you are doing with it.
It can mute your speakers in libraries. It can automatically put up the away message "Watching a DVD" when you are using the DVD Player. It can change your status messages to let your friends know where you are.
You can have IMLocation automatically run an Automator workflow, to do literally anything in response to where you are.
Your location is determined by the unique identifier (called the MAC address, although it is not related to Apple) of the wireless access point or ethernet jack you are using to connect to the internet. The first time you access the internet somewhere, IMLocation asks you to name where you are. The next time you go online there, IMLocation will know where you are, and can, for example, mute your speakers.
After downloading IMLocation, simply drag it where you want it installed, and run it.
By default IMLocation will start your status messages with your location, so the away message "working", will automatically become "Home: working". You can always turn off this option.
Mac OS X 10.5 on a laptop made by Apple.
Check the FAQ if you have more questions.