Here's four traditions you might come across in Sweden:
1: Crayfish Parties. You might get invited to one when you have friends here. I don't personally like boiled crayfish, because you need to do so much stuff (like take away the shell/whatever, etc.) before you can eat just a certain amount of meat in one crayfish.
Crayfish {photo from Wikipedia}
2: Midsummer. In mid-June school is out. It is an occasion of large gatherings. Many Swedes take advantage of this time to fulfil their social obligations. Swedes even celebrate "Midsummer Eve", always taking place on a Friday between the 19th to the 25th of June. It is advised to spend Midsummer's Eve at a countryside.
3: Sour Herrring. This dish is made by small Baltic herring, which are then salted and fermented. Sour herring has a strong, pungent smell of rotting fish. The traditional way of eating sour herring is with a piece of thin bread, butter the bread, place the herring, put something like an "almond-shaped potato" and some chopped onions before eating.
4: Sweden's National Day. On the 6th of June (a day before my birthday), the King and the Queen take part in a ceremony in Skansen (Click here to see that blog post). In 2005, the Swedish parliament voted to make this date a public holiday.
