Your question of folk and progressive music in Finland... difficult to define what is what. Here is something - and I will find out more.
Progressive bands from early 70's I remember:
Tasavallan Presidentti with Jukka Tolonen, guitar
Wigwam with Jim Pembroke, keyboards, song
Also:Piirpauke, Kalevala
http://www.youtube.com/watch?v=Muup_6I3wMs
http://www.youtube.com/watch?v=_6v4WIh_jNc
Folk music
http://www.fimic.fi/fimic/fimic.nsf/mainframe?readform&48AC42817E62B60542256B53003E87EB
Finnish Music Information Centre
Värttinä
http://www.youtube.com/watch?v=guDRZyJi2WQ (old)
http://www.youtube.com/watch?v=DClPMnQUaUk
http://www.youtube.com/watch?v=zEcDvSUZCeE
http://www.youtube.com/watch?v=l9ozxHOXf8I (Seelinnikoi, new)
Loituma
http://www.youtube.com/watch?v=vjvVBCNcL_A
Ultra Bra based to folk music, but new way of doing it, popular
http://www.youtube.com/watch?v=YYWjAukvK3E
http://www.youtube.com/watch?v=4x7bCVeMghY
Kaustinen Folk Music Festival
extracts from this year, funny
http://www.youtube.com/watch?v=kYga9BceJJU
http://www.youtube.com/watch?v=4x7bCVeMghY
Traditional you might enjoy:
Pihasoittajat Viulu-ukko Eurovision 1976
http://www.youtube.com/watch?v=CwKuS5_3ntU
http://www.youtube.com/watch?v=gaLL2z5zOx8 (the same in english)
Wimme, Maria Kalaniemi, JPP and
http://www.youtube.com/watch?v=iCmnkArGlZA
Kantele, example of its possible use
http://www.youtube.com/watch?v=7hATxM8lRLc
Tango
http://www.youtube.com/watch?v=s1l04PPO1GI
Olavi Virta:Punatukkaiselle tytölleni, picture of our nature, also in winter
Other
http://www.youtube.com/watch?v=_oyQtigdfao
Tapio Rautavaara Kulkurin iltatähti
I'll get back to the other kind of folk music... maybe Hector etc. and other favourites of mine