From the timetable at airBaltic's website:
http://www.airbaltic.com/upload_file/timetable.pdf
the Q400 operates to:
Aalesund, Belgrade, Berlin TXL, Billund, Brussels, Budapest (new route), Copenhaguen, Dusseldorf, Frankfurt, Hamburg, Helsinki, Kiev (not yet), Kittila, Kuopio, Lappeenranta, Lulea, Munich, Oslo, Oulu, Rovaniemi, St. Petersburg, Stockholm, Tampere, Tromso (not yet), Turku, Umea, Vaasa, Vienna, Zurich.
Add also: Vilnius, Tallin, Amsterdam, Kuusamo, Palanga, Kaunas..