For the Skien, Norway Show on 15 June ( http://www.stevneplassen.no/index.htm ), how do you get there from Oslo? Mass Transit like Train? Bus? Do I need to rent a Car? How far is it from Oslo?
Train is probably the easiest public transport. Expect something under 3,5 hours. It's about 200 kilometres from the airport. Or rent a car and take the E6/E18 motorway westbound. Should take about 2,5 hours.