The original post only has US helplines. I've added UK helplines underneath. It would be great if people could add numbers from everywhere in the world.
Depression Hotline:
1-630-482-9696
Suicide Hotline:
1-800-784-8433
LifeLine:
1-800-273-8255
Trevor Project:
1-866-488-7386
Sexuality Support:
1-800-246-7743
Eating Disorders Hotline:
1-847-831-3438
Rape and Sexual Assault:
1-800-656-4673
Grief Support:
1-650-321-5272
Runaway:
1-800-843-5200, 1-800-843-5678, 1-800-621-4000
Exhale:
After Abortion Hotline/Pro-Voice: 1-866-4394253
Child Abuse:
1-800-422-4453
UK Helplines:
Samaritans (for any problem):
08457909090 e-mail jo@samaritans.org
Childline (for anyone under 18 with any problem):
08001111
Mind infoline (mental health information):
0300 123 3393 e-mail: info@mind.org.uk
Mind legal advice (for people who need mental-health related legal advice):
0300 466 6463 legal@mind.org.uk
b-eat eating disorder support:
0845 634 14 14 (only open Mon-Fri 10.30am-8.30pm and Saturday 1pm-4.30pm) e-mail: help@b-eat.co.uk
b-eat youthline (for under 25's with eating disorders):