Looking for Folk/vikingish stuff...

Windir - I've only heard Arntor and it was a little boring
Mithotyn - Gathered Around the Oaken Table is enjoyable
Borknagar's s/t, but you said good production
Finntroll - their stuff is fun I guess
Skyforger - I like their folk album (not metal at all though, I hope that doesn't matter)
Amon Amarth - decent
Hellhammer - neither folk nor viking but listen anyway
 
KIUAS!

the new kiuas album is to release on the 27th. its a mix of folk and power metal with an agressive side to it. i have the "winter in june" EP and it nothing short of awesome. ill put their album in the top 10 of the year. the production is crystal clear too
~gR~
 
Check out these albums:

Empyrium - Songs Of Moors And Misty Fields
Hollenthon - Domus Mundi or With Vilest Of Worms To Dwell
Isengaard - Høstmørke
Primordial - Storm Before Calm or The Gathering Wilderness
Temnozor - Horizons

Plus a few folkish BM albums:

Ulver - Bergtatt (or Kveldssanger for pure folk)
Drudkh - Autumn aurora
 
Melodeath said:
apparently Asmegin.
Way to steal my band, sir.

also:

Aes Dana - La Chasse Sauvage
Cruachan - Folklore is my favorite
Mael Mordha (more doom-influenced)
Waylander - Reawakening Pride Once Lost is the only worthwhile listen.
Belenos (celtic/pagan black metal)
Pagan Reign - Ydeli Biloy Veri
Summoning - technically not "viking or folk" or whatever the hell you're looking for, but still worth mentioning. You already know them, though. Still..worth..mentioning..
have fun.