The websites of charities often contain much useful information including free reports (and other publications), guidance and statistics. Some of the most useful for the social sciences are listed below:

Children 

Barnardos - Charity which works to transform the lives of the most vulnerable children in society through their work, campaigns and research. 

NSPCC - Charity which fights to end child abuse in the UK. The site includes statistics and research publications. 

Homelessness 

Shelter - Charity which campaigns against bad housing and homelessness.

Mental Health 

Mind - Charity which provides advice and support to anyone experiencing a mental health problem. It campaigns to improve services, raise awareness and promote understanding. The site contains guides to support and services. 

Poverty 

Joseph Rowntree Foundation - Charity which works for social change by researching the root causes of social problems and developing solutions. Has lots of free research publications.