Oslo to Stockholm

1- Stockholm to Oslo by Air

You can get from Stockholm to Oslo with a quick, direct 1-hour flight. These flights depart several times daily, most offered by SAS and Norwegian. Roundtrip airline tickets from Stockholm to Oslo (and from Oslo to Stockholm) start around $150 but depending on the time of year, they sometimes offer ticket prices under $100. A fast option, but involves getting to the airport.

2- Stockholm to Oslo by Train

Taking the train from Stockholm to Oslo can cost less and you can reserve tickets online, but the trip takes longer. Expect travel times of 5-7 hours between Stockholm and Oslo. RailEurope offers unlimited train travel in Sweden and Norway.

The quickest (and priciest) between Oslo and Stockholm is a new high-speed train operating 2-3 times a day in each direction. Cheaper is Swedish Railways (SJ.se), where InterCity train tickets cost around SEK 300 one way. Adults traveling with SJ can bring 2 passengers under 15 for just SEK 5 per child. Those trains connect Stockholm with Oslo through a 6-7 hour trip

Source: about.com