Can I automate location changing so I don't have to drive the choice manually? Wondering is anyone knows of an application that can change settings on my Macbook Pro depending on the wireless networks it detects?

Ie, If I was at work, connect to the Work Wireless, Change default printer, chance location, change wallpaper etc. 

I seem to remember seeing an app at one stage, however after much Googling I cannot find it. 

Any help would be greatly appreciated!
AirPort Location** takes snapshots of the system settings you select and re-applies them the next time you use your machine at that location.

** Update Oct 2016: Airport location appears to be no longer maintained, but still available at [MacUpdate.com][2]. It may be limited to older versions of OS-X. The same site suggests [ControlPlane][3] provides similar functionality; I have not used it.