How can I quickly change DNS server I often like to use a non-network specific DNS server (like Google's public DNS 8.8.8.8).  However, many public wi-fi locations won't load their "terms of service, click here" page during the authorization process.  I suppose it is because my Macbook needs to look-up their web page, but is sending DNS requests to Google, which are blocked because I'm not yet authorized.

The quick fix is to delete the DNS server from the Network preference pane (Network / Advanced / DNS / Select / delete / clickety / click /GAAA) ...

... and then add it back after I'm authorized.

So, what I'm looking for is an easy way to specify my DNS server.  I'd love to run some service or app that would clear the DNS server list (ideally without needing me to select anything).  And then run it again to put my DNS server specifications back.

Can this be accomplished with some Applescripting?  Or a terminal command (that I could then wrap with Automator)?
Once you have setup different Network Loacations as per Adam Rice's solution, you can quickly switch between the locations using top menubar option "Apple > Location".