Mobilizer: location-based actions for Mac OS X
Mobilizer can determine your location in a few ways: when you select it manually via the Mobilizer app, when you're connected to a specific wireless SSID, when you receive an IP address from a specific DHCP server (good for wired networks), or even when your power adapter is connected.
When you're connected to a specific location, Mobilizer can then do a certain set of actions that you define. For instance, when you're at home you probably want your home printer to be the default (instead of your work printer). You may also want to disable your screensaver password since you're not worried about lurking coworkers using your machine at home.
Other available actions include the ability to mount a network share (so you could mount your work file server when you connect to your work network) and turning Bluetooth on/off.
Mobilizer lets you set a 'default location' option as a catch all, and you can of course have actions assigned to that location (maybe you only want a screensaver password enabled when you're not at a defined location).
[Via Apple Downloads]