World Advertising Research Centre: http://www.warc.com/
WARC.com is the largest single source of online intelligence for the marketing, advertising, media and research communities worldwide. The subscription-based service gathers together over 25,000 articles, case studies, research reports and summaries drawn from over 30 international sources covering all areas of marketing communications. Members can also access ad-spend statistics, demographic and economic data, plus consolidated global industry news, marketing communications best practice papers and expert editorials on current industry trends.

Institute of Practitioners in Advertising: http://www.ipa.co.uk
The IPA is the trade body and professional institute for leading agencies in the UK's advertising, media and marketing communications industry, covering the Creative, Direct Marketing, Healthcare, Media, New Media, Outdoor, Sales Promotion and Sponsorship sectors.

Nielsen Media Research: http://www.uk.nielsen.com/site/index.shtml
Nielsen Media Research provides comprehensive information available across all media platforms, matching creative execution to expenditure, volume and demographics. Some free case studies and press releases are available at the firm's site.

The Advertising Association (UK): http://www.adassoc.org.uk
The Advertising Association is a federation of 25 trade bodies representing the advertising and promotional marketing industries including advertisers, agencies, media and support services.

Advertising Standards Authority: http://www.asa.org.uk
The ASA is the independent, self-regulatory body for non-broadcast advertisements, sales promotions and direct marketing in the UK. The ASA administers the British Code of Advertising, Sales Promotion and Direct Marketing (The CAP Code) to ensure that advertisements are legal, decent, honest and truthful.

European Association of Communications Agencies: http://www.eaca.be/
The European Association of Communications Agencies (EACA) is a Brussels-based non-profit organisation whose mission is to represent full-service advertising and media agencies and agency associations in Europe. EACA aims to promote honest, effective advertising, high professional standards, and awareness of the contribution of advertising in a free market economy and to encourage close co-operation between agencies, advertisers and media in European advertising bodies.