A lot of that stuff is a mix of Norwegian, Swedish, or Finnish. Much of it is a load of folk-metal bands with varying degrees of folk and/or metal. Likewise some are pure folk and others pure metal. As you might guess, I owe a lot of it to my exploration of the metal scene... even a lot of the non-metal stuff, because there's a bit of overlap in the tastes of some of the fans. Also, a good bit of it comes from searching the Scandinavian section of the world/folk section of mp3.com. It's fucking hard to find because they hide it pretty well under a load of subdirectories, but it's there.
If you're looking more for folk sounding stuff, I'd reccomend Hagalaz Runedance, Gjallarhorn, Hedningarna, Kari Rueslattan (her earlier stuff, anyway), and the stuff from mp3.com. Otyg and Lumsk are really really good as well, and they straddle the border of folk and metal pretty evenly. Then there's Storm, Thyrfing (though I'm not so fond of them overall), and Vintersorg's earlier material which is slightly more metal than folk, and then you have Finntroll and Moonsorrow who pretty much make insane finnish polka metal. (I love a band where I can say "Here comes the accordion solo!")
So there you go... part of the mystery unraveled for you. Personally I'm a big Otyg/Vintersorg/Finntroll kind of guy, but I have moods for lots of different things. I'm pretty sure you've got a load of related music that I've never heard of either, so spit it out... let's hear about 'em! Forum, e-mail, whatever.
