General population:
Mental health and psychological resilience during the COVID-19 pandemic (WHO Europe)
How to look after your mental health during the Coronavirus outbreak (Mental Health Foundation UK)
Special groups:
My hero is you: how children can fight COVID-19! (IASC MHPSS RG) is a story book that aims to help children understand and come to terms with COVID-19, and it is available in 38 languages.
You can find the version of the story book in the other languages at https://interagencystandingcommittee.org/iasc-reference-group-mental-health-and-psychosocial-support-emergency-settings/my-hero-you
Factsheets:
Recommendations for psychological support in response to coronavirus pandemic
Covid-19 stressors during the corona virus pandemic
Mental health and psychological symptoms as a result of the coronavirus pandemic Part 1 Part 2
Posttraumatic stress disorder - PTSD Part 1 Part 2
Brief history of trauma Part 1 Part 2
Short tips:
Coronavirus Disease 2019: Stress & Coping (Centers for Disease Control and Prevention)
Tips on how to cope if you are worried about Coronavirus and in isolation (NHS Scotland)
Coping with stress during the 2019-nCoV outbreak (WHO)
Keeping your distance to stay safe (APA)
Helping children cope with stress during the 2019-nCoV outbreak (WHO)