President Obama today signed a bipartisan bill into law that allows consumers to switch cell phone service providers without paying for a new phone. The Unlocking Consumer Choice and Wireless Competition Act reverses a decision made by the Library of Congress two years ago that made it illegal to "unlock" phones for use on other networks without the OK of your service provider, which meant companies like AT&T, Verizon, or Sprint could keep your phone "locked"– switching carriers or trying to link to other carriers overseas while traveling in that scenario was prohibitively expensive.
Here's background on the bill.