Kon-Tiki Kitchen, ☎ +47 64811616. Restaurant in the international terminal. Serves some pre-made hot meals for 119 (small portion) /159 (huge portion) NOK. Not too tasty, but works. On the second floor there's both power and free internet (Ask the cashier for username/password)edit
Gardermoen Hotel B&B is an airport hotel, 10 min drive from the airport. In June 2008 the price was 1800 NOK for two double rooms with a pick-up and drop-off service to the airport of 4 persons, breakfast included. You can book a pick-up and drop-off service separately for 45 NOK/person.
If you have more than a couple of hours between flights, Oslo is within reach by the Airport Express Train. A somewhat closer, and cheaper, option is Eidsvoll, a lakeside town where the Norwegian constitution came to light.