From the New Oxford American Dictionary:
"In general, different from is the construction most often used in the U.S. and Britain, although different than (used almost exclusively in North America) is also used, esp. in speech. Different from can sometimes lead to wordy constructions, whereas different than implies a comparison that from usually does not. . . Different to is common in Britain, but sounds strange to American ears. Than is more often acceptable when following the adverb differently, but still implies a comparison."