<map lat='59.20722764436484' lng='9.622306823730469' zoom='11' view='3' float='right' /> Skien is a city in Telemark, Norway. It's the capital of the county. Famous for Henrik Ibsen, most things there are also named after him. It has a population of 51 369.
If going towards Oslo you might want to head towards the railwaystation. This is the area called Nylende. From here you will be close to the beginning of the Rv 32 (This is a more direct route towards Oslo) going to Siljan. This way you will probably pass through Drammen on your way to Oslo. If going to Tønsberg, or Oslo by the coastline, it is advisable that you take a local bus that leaves you close to Telemarksporten. This is in Porsgrunn/Eidanger.
See Metrobuss for information on bus routes.
Also check NSB for train schedules. Notice that Skien and Porsgrunn are pretty much left out of the railwayplans of NSB, so they are usually buses between Skien/Porsgrunn and Larvik. There buses are operated by Nor-Way. They also have independent buses to Oslo, using the Rv 32 road.