A brilliant organisation that offers free online training about how to speak to someone you might be concerned with. It only takes 20 minutes to do, its free and it really could help you save someones life.
The International Association for Suicide Prevention
If you're based in a country or region that isn't covered by any of these resources then try this organisation. They have global scope and their website provides information on help available all across the world.
Hub of hope has a database of all kinds of different organisations that help with all kinds of mental health issues from substance problems to eating disorders and everything in between and the brilliant thing is that you can put in your location and find what's available near you.