Updated and separated list based on Artificial Intelligence in Finland post. The listing isn't systematic, but updated by AI events, publications etc. I am more than happy include new people (PhD student and above) to the list, ping @Twitter.

Organisations, research groups

Academy of Finland - Novel Applications of Artificial Intelligence in Physical Sciences and Engineering Research
http://www.aka.fi/en/research-and-science-policy/academy-programmes/upcoming-programmes/ai2/

Cognitive Science in University of Helsinki
http://www.helsinki.fi/kognitiotiede/english/staff/index.htm

Racisms and public communications in the hybrid media environment (HYBRA)
http://www.uta.fi/cmt/en/research/comet/projects/racisms.html

Helsinki Institute For Information Technology
https://www.hiit.fi/

Finnish Center for Artificial Intelligence
http://www.fcai.fi/​

Finnish Centre of Excellence in Computational Inference Research
http://research.cs.aalto.fi/coin/index.shtml

Language Technology Documentation Centre in Finland
https://kitwiki.csc.fi/twiki/bin/view/FiLT/PeopleEn

The Power of Algorithms research - studying the societal impact of machine decision making
https://algoritmitutkimus.fi/tutkimushanke/

RiskLab
https://risklab.fi/

User Interfaces Aalto University
http://userinterfaces.aalto.fi/

Moralities of Intelligent Machines
https://www.facebook.com/MachineMoralities/

Rajapinta - Researching digital
https://rajapinta.co/

Tech: computer science, mathematics, physics

Ville Kyrki
https://people.aalto.fi/index.html?profilepage=isfor#!ville_kyrki
Robotics, robotics vision.

Perttu Hämäläinen
https://mediatech.aalto.fi/~phamalainen/

Teuvo Kohonen
https://people.aalto.fi/index.html?profilepage=isfor#!teuvo_kohonen

Mikko Kurimo
https://users.ics.aalto.fi/mikkok/
Speech and language processing

Arto Klami
https://www.cs.helsinki.fi/u/aklami/
Multi-source probabilistic inference

Tapani Raiko
https://users.ics.aalto.fi/praiko/
Reinforcement learning

Erkki Oja
https://users.ics.aalto.fi/oja/
F.ex. Neural networks, unsupervised learning, computer vision

Timo Honkela
https://tuhat.helsinki.fi/portal/fi/persons/timo-honkela(2c6425cd-0cdb-4775-987c-6f3bfe9e96a5).html

Harri Valpola
The Curious AI Company
http://valpola.kapsi.fi/publications/

Antti Tarvainen
The ​Curious AI Company

Dorota Glowacka
https://tuhat.helsinki.fi/portal/en/persons/dorota-glowacka(7661275e-b717-4cea-92b6-04e117f18cdb).html

Hannu Toivonen 
Computer science
https://www.cs.helsinki.fi/u/htoivone/

Sasu Tarkoma
Computer science
https://www.cs.helsinki.fi/u/starkoma/

Teemu Roos
Computer science
https://www.cs.helsinki.fi/u/ttonteri/

Ella Peltonen
Computer science
https://www.cs.helsinki.fi/u/peltoel/

Samuel Rönnqvist
Computer Science
https://scholar.google.fi/citations?user=EJKJjcAAAAAJ&hl=fi

Petteri Kaski
Computer Science
https://users.ics.aalto.fi/pkaski/

Lu Cheng
Computer Science
https://people.aalto.fi/new/lu.cheng

Baris Serim
Computer Science
https://tuhat.helsinki.fi/portal/en/persons/baris-serim(b0d2e355-4b3c-47ec-baf0-99bda1be92f8).html

Alex Jung
Computer Science, machine learning
https://people.aalto.fi/alex_jung

Anna Kantosalo
Computer Science
https://tuhat.helsinki.fi/portal/en/persons/anna-kantosalo(dc0fa396-3bca-44a3-88fd-d2d3b25b815e).html

Leo Leppänen
Computer Science
https://tuhat.helsinki.fi/portal/en/persons/leo-leppanen(44db41eb-93ae-44c9-8350-8b9b9df99cb0).html

Susanna Pirttikangas
Computer science, mathematics
http://www.ee.oulu.fi/~msp/#

Jussi Rintanen
Computer science
https://users.aalto.fi/~rintanj1/

Vishal Singh
Computer Science
https://people.aalto.fi/new/vishal.singh

Jonathan P. F. Strahl
https://users.ics.aalto.fi/jstrahl/

Jörg Tiedemann
Computer science, linguistics
https://tuhat.helsinki.fi/portal/en/persons/joerg-tiedemann(246633aa-0fd1-4f2b-bb8e-8b2c894decc2).html

Valeriy Vyatkin
Professor, Electrical Engineering and Automation
https://people.aalto.fi/new/valeriy.vyatkin

Keijo Heljanko
Professor, Computer Science
https://people.aalto.fi/index.html?profilepage=isfor#!keijo_heljanko

Cognitive science, psychology

Otto Lappi
Cognitive science
http://www.mv.helsinki.fi/home/olappi/

Anna-Mari Rusanen
Cognitive science
https://tuhat.helsinki.fi/portal/fi/persons/annamari-rusanen(cab74ea2-965a-4afa-b8fe-d069766c691c).html

Petri Ylikoski
Social sciences
http://blogs.helsinki.fi/pylikosk/

Michael Laakasuo
Cognitive science
http://www.helsinki.fi/kognitiotiede/henkil/

Minna Huotilainen
Cognitive science
https://tuhat.helsinki.fi/portal/fi/person/huotilai

Ville Harjunen
Social psychology
https://tuhat.helsinki.fi/portal/en/persons/ville-johannes-harj(f30fb290-0564-49df-8304-6c49700c6dce).html​
 

Social sciences, philosophy, law

Arto Laitinen
Philosophy
http://www.uta.fi/yky/fil/yhteystiedot/artolaitinen/index.html

Raul Hakli
Social and moral philosophy
https://tuhat.helsinki.fi/portal/en/persons/raul-hakli(7bcdbd00-b65e-45fc-a10a-892efd14e70a)/publications.html

Samuli Reijula
Social and moral philosophy
https://samulipoyhonen.wordpress.com/

Vesa Kyyrönen
Law

Ali Imran
Law
https://www.utu.fi/en/units/law/faculty/people/Pages/ali-imran.aspx

Business, economics

Peter Sarlin
https://www.hanken.fi/en/person/peter-sarlin

Tapio Vepsäläinen
https://research.utu.fi/converis/portal/Person/732642?auxfun=&lang=en_GB

Valtteri Kaartemo
https://research.utu.fi/converis/portal/Person/1057055?auxfun=&lang=en_GB

Military science

Martti Lehto, University of Jyväskylä