No offence here Draugen, but Mellanöl is actually a whole other thing than Folköl
Mellanöl is above folköl in strength, but below starköl (hence the name) that is, it is around 4.5 %. It was sold in ordinary shops until the late 70´s, but was then removed due to the abuse of it, it was almost only younger ppl drinking it. It can now be bought at systembolaget.
Trivia: The best mellanöl is TT (which can also be bought in stronger and weaker version, but none of them are as good as the mellanöl, all of this obviously IMHO).
The danish class one, the pilsner, is the equal of the swedish mellanöl, with classic brands such as "Carlsberg Hof" and "Tuborg Grön".
Apart from all this I must say that folköl can be really great sometimes, like in a park in summer, but the taste is actually quite... watery.
-phyros ( did I mention I like beer? )