If you have a limited income, you may be eligible to apply for council housing, or for housing through a housing association. You can find more information about both of these options at www.direct.gov.uk
Councils all have their own rules about who qualifies for a council house or flat. If you are eligible, you may not get a house straightaway as councils prioritise people according to a number of different factors, for example whether someone is homeless or living in unhygienic conditions. If you would like to apply for a council house, you need to contact your local council and request an application form. As long as you complete the application form correctly, the council must consider your application.
Housing associations are one type of Registered Social Landlord, or "RSL". Co-operatives, trusts and companies can also be RSLs. RSLs are designed to help people who are in 'housing need', but each RSL has its own rules about the type of housing service they provide and who can apply. You can ask for a written copy of these rules. RSLs take the majority of their new tenants from the local council's housing waiting list, so it is sensible to contact the council first.