Most of these links have full or partial English translations, making this a great place to start searching.

General Swedish Folk Music Links

The Orsa style in perspective: By Anders Rosén
Rootsworld: Scandinavian Music Reviews
Swedish Music Information Center: Read about Swedish composers.

Mostly Nordic Instruments

Hurdy-gurdy: A written introduction by Alden and Cali Hackmann.
Härjedalspipan: a traditional Swedish flute, similar to the Spelåpipa.
Paul Wilson's fiddles: a cross between Italian and Norwegian ideas.
Swedish bagpipes: Written by Olle Gällmo
NSAA Forum: Norden Säckpipa Association of the Americas
More on Swedish bagpipes: from nyckelharpa player Sean Fulsom.

Nyckelharpa Mingling with Other Traditions

Rasa: Music based on Indian bhajans, featuring a nyckelharpa
Wherligig: Celtic and Nordic Music