Virgin America just became the first airline to offer WiFi on all of the flights in its fleet. VA uses the Gogo In-Flight service to provide onboard internet access, the rates are based on the length of the flight.
In April I wrote my first blog post from 37,000 feet on a Virgin America flight from SFO to LAX.
Hopefully more airlines will follow this example in the near future by equipping their entire fleet. A few airlines have already started the process.