http://www.pp-international.net/
Hit up that link, and look down the list on the right for your country's local party.
For people who can't be bothered, very basically Pirate Parties stand for freedom of information, open culture, reform of the intellectual property system, and, in the UK at least, reducing the excessive surveillance.
The Swedish one is the third biggest there, and they have two seats in the European Parliament.
I personally support them, because their policies facilitate the direction of modern technology and how it's being used.
What's your opinion of them?