CREA.net [ http://www.crea.net/ ]
Real estate site exclusively for the less than 45,000 real estate agents who have acheived the 'Certifed Real Estate Agent' status.

National Association of Estate Agents (NAEA) [ http://www.naea.co.uk/ ]
Professional body for estate agency. Its 10,000 members practice across all aspects of property both in the UK and overseas, including residential and commercial sales and letting, property management, business transfer, auctioneering and land.