There are over 400 stat posts on DMR. Browse the full list here.
The airlines that will be offering you a chance to stay in touch with your friends are Virgin America, United Airlines, American Airlines, Delta, AirTran, US Airways and Alaska Airlines.
This appears to be a marketing effort to expose more travelers to in-flight wifi by offering up free access to the number one, most accessed website via Gogo. It is unclear what continued access will cost after the monthly promotion is over, but Gogo regularly charges between $4.95-$12.95 for access, depending on the length of flight.