Unlock Your Phone By Sascha Segan Unlock your cell phonenot just for yourself, but for all of us. A recent Copyright Office ruling gave the thumbs-up to unlocking cell phones, including the GSM phones that are used by Cingular, T-Mobile, and most of the rest of the world outside the U.S. Unlocking phones lets you use phones bought from anyone with any GSM carrier, including foreign ones. It opens up a huge market for used phones. And just as important, it sends a message to wireless carriers that we're tired of having them control our phone choices. Sadly, this ruling doesn't affect Alltel, Sprint, or Verizon customers, whose phones must be approved by their networksand the networks don't approve phones they didn't sell. But if you''re with Cingular or T-Mobile, go for it. SLIDESHOW (5) Slideshow All Shots Unlock By Request If you've had a T-Mobile phone for 90 days, or you've run out of time on a Cingular contract, you can get an unlocking code just...