Legal-Explanations.com
"the very best in free legal resources written in plain English. Our website currently contains over 2,500 legal definitions and will be expanded in coming months to include a vast collection of legal resources." However, being US-based, some of the definitions can be misleading if applied outside their US context. For example, the site offers three definitions of "voir dire": the first refers to the peculiar US practice of allowing prospective jurors to be interrogated by counsel; the third definition is closest to (but not a precisely accurate definition of) the meaning given to this expression in other Common Law jurisdictions. Attempts to define expressions used in English courts are sometimes painfully deficient: thus, for instance, "Queen's Bench" is defined as meaning "the highest court in Great Britain during the reign of a Queen", whereas (of course) the Court of Queen's Bench - now the Queen's Bench Division of the High Court - operates only in England and Wales (not throughout the United Kingdom), and is not the highest court (being subject to appeals to the Court of Appeal and, ultimately, the House of Lords). Still, a very useful resource if used with caution.

Oran's Dictionary of the Law
American. One of the better on-line legal dictionaries.

Merriam-Webster's Dictionary of Law
Includes "some 10,000 legal terms, pronunciations and legal definitions".

Law.com Dictionary
Based on the "Real Life Dictionary of the Law".

The 'Lectric Law Lexicon
Claims to be "the Net's Most Extensive Legal Dictionary". But the standard of scholarship may be judged from this remark: "there are occasional Latin and obsolete terms that we left in though we have no idea what they mean, so don't ask".

Anderson's Dictionary and Compendium of American and English Jurisprudence 1893
A learned work, of mainly (but not merely) historical interest.

Bouviers Law Dictionary 1856 Edition
A great American legal dictionary; but its age limits its usefulness.

Bouviers Law Dictionary 1856 Edition
Same dictionary, different URL.

Duhaime's Law Dictionary
A "plain English" glossary of legal terms.

Nolo's Law Dictionary
Another "plain English" glossary of legal terms.

Court TV Law Centre Glossary
Pitched at a level appropriate to viewers of a cable television network given over exclusively to televising court-room dramas, both real and fictional.

xrefer
Searchable interface for reference resources including A Dictionary of Business (OUP), A Dictionary of Law (OUP), Dictionary of Accounting (OUP), Penguin Business Dictionary, Penguin Dictionary of Economics, Penguin International Dictionary of Finance, etc.

Legal Dictionary Links