Apostrophe Protection Society

Promotes the correct use of apostrophes in all forms of text written in English.
http://www.apostrophe.org.uk/

Health Literacy Group

Funded by the Department of Health and the Department for Innovations, Universities and Skills, the Health Literacy Group is free to join. The group is keen to link with others with an interest in health literacy, in the UK and abroad. 
http://www.healthliteracy.org.uk/

‘How to write clearly’ (European Commission)

This booklet supports the EC’s Clear Writing campaign and contains many before-and-after examples. It draws on parts of Martin Cutts’s book ‘The Oxford Guide to Plain English’. 
http://ec.europa.eu/translation/writing/clear_writing/how_to_write_clearly_en.pdf

Information Design Association

A group of information designers and other professionals in the UK with an interest in information design (of which plain language is an important part). 
http://www.informationdesignassociation.org/

Local Government Improvement & Development

This organization – previously the Improvement and Development Agency – ‘supports improvement and innovation in local government, focusing on the issues that are important to councils and using tried and tested ways of working’. The website includes a large ‘Knowledge’ section, with information on plain English in local government. 
http://www.idea.gov.uk/idk/core/page.do?pageId=8021380