Im really suprised no one has mentioned my home town Göteborg yet. Göteborg is awesome during the summer. We also got a festival called "The Gothenburg Party" basicly the entire city gets shut down and there is beer/resturant/party tents all over the the town and ppl just walk from one tent to another entire day and night.
The nightlife in Göteborg is pretty damn good too but it aint no Bangkok/Amsterdam/New York but there plenty off clubs to choice from and there is alot of hot girls. ;)
Also you can easily go by boat (with your car) from Denmark(Fredrikshavn) too Göteborg then you if you want to go up to Oslo it´s just 25miles from Göteborg and
a excellent highway between the too cities.
If you want a to hook up in Göteborg or just want more info hit me up on icq . Im also pretty much as young as you. ;)