IT Explained for start ups and growing businesses - from buying a computer, to using social networking sites for business to selling online.
The main functions of Companies House are to: incorporate and dissolve limited companies; examine and store company information delivered under the Companies Act and related legislation; and make this information available to the public. 

However you can also research company, start a company, change your company details, file your annual return / accounts and close a company down. There is also general guidance area plus a great 'forms' section

Enterprisenation.com is a free resource to help you start and grow your business at home.
Formerly called Inland Revenue. Has information for businesses, employers and individuals - tax, employment, VAT etc.
NESTA is the National Endowment for Science, Technology and the Arts - an independent body with a mission to make the UK more innovative. Their endowment status means we operate at no cost to the UK taxpayer. They invest in early-stage companies, inform policy, and deliver practical programmes that inspire others to solve the big challenges of the future
NetRegs provides free environmental guidance for small businesses in the UK, helping you to understand what you need to do to comply with environmental legislation and protect the environment.
The official government body responsible for granting Intellectual Property (IP) rights in the United Kingdom (UK). These rights include: Patents, Designs, Trade marks and Copyright