Many of these cottages are open all year round, also in the winter:

Aavasaksan Aurinkomajat: http://www.aavasaksanaurinkomaja.com

Ahoniemi (near Joensuu): http://www.ahoniemi.com

Aito Mökkiloma - Cottage Vacation (Mokkiloma.net, Cottagevacation.net, is a service, where users can search for cottages located in Finland and rent them directly from the owner. The service has advanced search features, which makes it easy to find cottages that fit your needs. Feel free to explore!): http://www.mokkiloma.net/english.htm

Alatalo Cottage (Padasjoki, Lahti region): http://www.kolumbus.fi/rauno.hannikainen/

Anttila Holiday (60 km from Tampere): http://www.salkolahti.com/index.php?sivu=&lang=en

Arctic Circle cottages: http://www.polar-blue.fi/saarituvat/index.html

Aurantola Holiday Resort (Jaala, Kouvola region): http://www.aurantola.fi/aurantola_frames_uk.htm

Aurinkoranta (Asikkala, Lahti region): http://www.aurinkoranta.net

BlueWhite Resorts (cottages, fishing, safaris, Carelia Border Area): http://www.bluewhite.fi

Car Rental Bevari (rent a car and a cottage from the same office at many Finnish airports): http://www.carrentalbevari.fi/default.asp?Lang=13 

Cosy Finland - cosy home meals in Finnish homes, visits to cottages & saunas: http://www.cosyfinland.com

Cottage Holidays (Savonlinna region): http://www.cottageholidays.fi/eng/index.htm

Cottages in Iso-Syöte National Park region: http://www.syote.net/default_eng.php

Cottages in Kuusamo (Lapland): http://www.koillismaa.fi/~knet1053/, http://www.geocities.com/ihtiandre/, http://personal.inet.fi/yritys/lomatuulia/

Cottages in Tampere region: http://www.mokkiavain.fi/english/

Cottage Village Kerimaa: http://www.kerimaa.net

Ekenäs (southernmost Finland): http://www.etelakarki.com/Englanti/mokkilomat.asp

Eteläpää (Siikainen): http://www.etelapaa.fi/en/etusivu.html

Experience Yard Pikkukili (between Joensuu and Lieksa in Eastern Finland, accommodation in log houses, riding, children`s playground, domestic animal zoo): http://www.matfuturevision.fi/pikkukili/english/accommodation.htm

Family Holiday Resort Pajarinhovi (Zoo, hotel, cabins in Kitee): http://www.pajarinhovi.fi

Finnish Lakeside Cabins: http://www.finnishlakesidecabins.com

Hattusaaren Rantamajat (Eastern Finland): http://www.hattusaarenrantamajat.net/

Heikin Tupa (150 km from Jyväskylä): http://personal.inet.fi/yritys/heikintupa/

Heikkinen (near Kuopio): http://personal.inet.fi/yritys/heikkisen.lomamokit/

Heinäsaari (Heinola, Lahti region): http://www.heinasaari.com

Herrankukkaro in Rymättylä, the archipelago of Turku (Old fisherman's village for groups, min 8 persons. Recommended for weddings!): http://www.herrankukkaro.fi

Himosmökit: http://www.himosmokit.com

Hoimela (Asikkala): http://www.hoimela.com

Holiday Club: http://www.holidayclub.fi/

Holiday: http://www.huvila.net

Hossa Holiday Centre (rooms & cottages): http://www.hossanlomakeskus.com/english.htm

Hämeenlinna: http://www.htk.fi/hts/cottages

Jaakkolan Mökit (Vuokatti): http://www.jaakkolanmokitvuokatti.fi/enindex.htm

Jokikumpu (Nilsiä): http://www.jokikumpu.com/en/

Jokiniemi (between Kuopio and Iisalmi - very beautiful location!): http://www.jokiniemenlomamokit.fi/indexE.html

Jänisvaara's Bio-Farm (Koli, Eastern Finland): http://www.maatilamatkailu.fi/eng/

Järvisydän Holiday Village (Rantasalmi): http://www.jarvisydan.fi/JARVISYDAN/ENGLISH/index.html

Kaartila (Mikkeli): http://www.kaartila.com

Kaavi Holiday Village: http://www.kaavilomakeskus.fi/

Kajaste Holiday (Eastern Finland): http://www.kajaste.com

Kalajoki Luxurious Holiday Apartments: http://www.hiekkasarkat.com

Kapiainen Holiday (200 km north of Helsinki): http://personal.inet.fi/yritys/kapiaisen.lomamokit/english/indexen.htm

Karhupirtit (Taipalsaari - Lappeenranta): http://www.karhupirtit.com

Karjalan Helmi (Pearl of Karelia, Eastern Finland): http://www.oppivat.net/~karjalanhelmi/eng/index.htm

Kesäranta (Ruokolahti, Eastern Finland): http://www.kesaranta.com

Kievarireitti: http://www.kievarireitti.fi/eng/

Kiviniemi (Savitaipale, 200 km from Helsinki): http://www.savitaipale.fi/kiviniemi/english/index.html

Korintti luxury holiday apartments: http://korintti.siteyard.com/eng/cfmldocs/index.cfm

Korvenkehto: http://www.korvenkehtolomamokit.fi

Lahdenrannan Loma (Heinävesi): http://www.lahdenrannanloma-asunnot.info/

Lake Karelia (Eastern Finland): http://www.lakekarelia.fi

Laurila (Lempäälä): http://www.saunalahti.fi/hein/

Lehmonkärki, cottages & VIP Villa (Asikkala, Lahti region): http://www.lehmonkarki.fi

Leisure Centre Mannilanniemi (Puumala, Eastern Finland): http://www.mannilanniemi.com

Lempivaara Camping (Riihimäki): http://www.lempivaara.com

Leppävirran Niemilomat (cottages in Varkaus surrounded by peaceful nature and beautiful scenery): http://www.leppavirranniemilomat.fi

Loikansaari Cottages (Savonlinna): http://www.loikansaari.fi

Lomakivi Quality Vacation Cottages (Kausala, Kouvola region): http://www.lomakivi.com/english/index.html

Lomamökkilä (Savonlinna): http://www.lomamokkila.fi/index.php?lang=en

Loma-Perkkiö (cottages in Kajaani, apartments in Vuokatti): http://www.lomaperkkio.com/eindex.html

Lomarengas (Finnish Countryside Holidays - over 1000 cottages, bed & breakfast, farm holidays): http://www.lomarengas.fi

Loma-Rinteelä (Vuokatti): http://www.lomarinteela.net

Loma-Ässä: http://personal.inet.fi/yritys/loma-assa/e/index.html

Lomso (Houtskär, Turunmaa archipelago): http://www.lomso.com

Martinselkonen Wilds Center: http://www.martinselkosenerakeskus.com

Mattila Farm (180 km from Helsinki): http://www.lomatila.com/english.html

Merenlahti (Lake Saimaa, Lappeenranta): http://www.merenlahti.com

Meri-Huvilat: http://www.merihuvilat.com