Believe it or not, there's an upside to the rapid release of smartphones that seems to have become the norm: the old models, barely out of their prime when a replacement comes along, have their prices viciously cut. Sometimes to nothing. Take the Google Nexus S, for example. When it came out last year, it was hailed as the Android phone to get. A year later, no one even talks about it as the all-new Samsung Galaxy Nexus has become the new Google Phone. Now you can get the Nexus S for nothing but your signature. It's crazy. Even crazier is that there are a number of good phones you can cop for free (with a two-year contract). Take a look.