If you want to set your Mac OS X Location automatically (based on Airport name (SSID) or something else), have a look at this script and launchd item.
Basically, it creates a launchd item that listens for changes in the /Library -> Preferences -> SystemConfiguration directory. And it happens that this directory gets changed every time the network changes. When a change is noticed, a script launches that figures out the SSID and IP addresses, and from there sets the Location based on some rules.
Because the script is simply a bash script, you can make it do lots of stuff based on your current location
[robg adds: I haven't tested this one...]

