UK Intellectual Property Office Trade Marks Database (http://www.ipo.gov.uk/tm/t-find/t-find-text.htm)
Covers UK trade marks, UK designated marks under the Madrid protocol (M prefix) and Community trade marks (E prefix)

TMView (http://www.tmview.europa.eu/tmview/welcome.html)
A free all-in-one trade mark search facility. Covers 6 national offices including the UK plus Community trade marks and Madrid Agreement trade marks. It is aiming to cover all 27 national European trade mark offices by 2011, in addition to Community trade marks and Madrid Agreement trade marks - about 8.5 million trade marks.

Community Trade Marks On-line (http://oami.europa.eu/CTMOnline/RequestManager/de_SearchBasic?transition=start&source=Log-in.html&language=en&application=CTMOnline)
Database of European Community Trade Marks. Advanced search available-click on the two magnifying glasses symbol.

Romarin (Madrid Agreement) (http://www.wipo.int/romarin/)
Database of Madrid Agreement trade marks applications with detailed status information

International Trade Mark Classification (http://www.wipo.int/classifications/en/)
The Nice Agreement classification scheme covering the kinds of products and services being trade marked.

Other trade mark databases and information websites (http://www.bl.uk/reshelp/findhelpsubject/busmanlaw/ip/tradmk/iptmdatabses/databases.html)
Concentrates on databases and official gazettes in trade marks, both free and priced, from anywhere in the world, plus domain names material. For other material, British and European sources are favoured. Maintained by the British Library