The Best of British: The American's Guide to Speaking British  
   The differences between American and British English, explored by a Brit living in Texas.
   http://www.effingpot.com/

The American-British - British-American Dictionary  
   Collection of words and phrases, including information about holidays, weights and measures, money, area codes and presidents and prime ministers.
   http://www.peak.org/~jeremy/dictionary/dict.html

United Kingdom English for the American Novice  
   Words and phrases that may cause problems for American visitors.
   http://www.hps.com/~tpg/ukdict/

British-American Dictionary  
   An easy to read, humorous translation of British English to American English
   http://www.travelfurther.net/dictionaries/british-american.htm

Holiday Inn UK - I Say Tomato  
   American-British travel dictionary and a few dozen British to American translations.
   http://www.holiday-inn.co.uk/ISayTomato.shtml

English Usage in the UK and USA  
   A light-hearted look at some differences between English as spoken on both sides of the Atlantic.
   http://www.krysstal.com/ukandusa.html

WWlib - Notes on American English  
   Tabular presentation of the differences between American and British English, with a thorough explanation of cultural/technical differences when necessary. Expressions specific to Canada are also noted.
   http://www.scit.wlv.ac.uk/~jphb/american.html

American Dialect Society List Archives  
   A web-searchable archive of the recent postings to the ADS-L archive.
   http://listserv.linguistlist.org/archives/ads-l.html