The Journal of Open Psychology Data (JOPD) publishes peer-reviewed data papers describing psychology datasets with high reuse potential. Data papers may describe datasets from unpublished work or from papers published previously in a traditional journal.
A list of 100 free, large datasets not including repositories, and there's some metadata about what they contain and how easy they are to use.
Mental Health & Well-being
MentalHealth.gov — A resource provided by the U.S. Department of Health & Human services, MentalHealth.gov provides one-stop access to U.S. government mental health and mental health problems information.
GoodTherapy.org — An online therapist directory compiled by an association of mental health professionals from more than 30 countries worldwide who support efforts to reduce harm in therapy.
APA Psychology Help Center — A listing of articles and mental health interest areas as well as resources for finding mental health professionals.