Guidestar UK
A charity providing information about UK charities. Some of this comes from information in the public domain, and some is supplied by the charities themselves.

KnowHow NonProfit
KnowHow NonProfit is a resource for building and sharing expertise in non profit and charity organisations, community groups, faith groups and campaigning organisations.

The Charity Commission for England and Wales
Government organisation that is the regulator and registrar for charities in England and Wales. Includes information on each charity, how to register a charity, guidance for charities, complaints procedures, information about the commission, and more.