Helsinki, Finland (the land of Linux, MySQL, IRC) has quite a lot, to sample few:
Jolla (smartphone)
Web of Trust (used fe. by Facebook)
Music Kickup (revolutionizing the music industry)
Upcloud (Amazon AWS competitor)
Transfluent (best of breed translation services, used fe. Barack Obama)
Ovelin (best of breed music learning games)
Applifier (best of breed game capturing & sharing system)
ZenRobotics (robotic construction waste recycling automation)
Indoor Atlas (ground breaking magnetic navigation system)

Of course the gaming scene is boomin’
Rovio (do I need to say more? :D)
Supercell (highest grossing mobile game ever – Clash of Clans)
Frogmind (Badlands, awarded by Apple as best of breed on iOS)
Grand Cru (Supernauts – Sort of Minecraft meet Sims hybrid)
Umbra Software (best of breed visibility solutions)

One could add Fingersoft (Hill Climg Racing, recently made 12+ million euros) to the gaming scene as well, though it’s not from southern Finland.