General Letting Sites

• Rightmove.co.uk
• The Letting Network
• Simple2Rent.co.uk

Professional Bodies

• Association of Independent Inventory Clerks (AIIC)
• Association of Residential Letting Agents (ARLA)
• Association of Residential Management Agents (ARMA)
• National Approved Letting Scheme (NALS)
• National Association of Estate Agents (NAEA)
• Royal Institution of Chartered Surveyors (RICS)
• UK Association of Letting Agents (UKALA)

Landlords' Associations

• National Federation of Residential Landlords
• National Landlords' Association
• Residential Landlords' Association

General Housing Advice and Housing Advice Agencies

• Citizens' Advice Bureau
• Shelter
• In Small Print.co.uk
  

Insurance Services

• Alan Boswell Insurance
• HomeLet
• Letsure
• UKinsurance NET
  

Tenant Referencing Services

• Experian Tenant Verifier
• TICA (UK) Ltd

Letting and Property Management Software

• Aspasia
• Carl Communications
• CFP Software Ltd
• EZPZ Software
• GMW Systems
• Key-Data Systems
  
• Multi-User Systems Ltd
• Proman Technology Services
• Rentman
• Websky Ltd

Relocation Advice and Information 

• Association of Relocation Professionals
• Advisory Centre for Education

Professional Training

• ARLA/NAEA
• Farndon Estates
• Training for Professionals 

• Association of Independent Inventory Clerks
  
• Castle Inventories
  

Government Bodies

• Housing Corporation   - regulates, funds and promotes the proper performance of registered social landlords
• Department for Communities &Local Government (DCLG)