American Dialect Society List Archives: A web-searchable archive of the recent postings to the ADS-L archive.
British-American Dictionary: An easy to read, humorous translation of British English to American English
English Usage in the UK and USA: A light-hearted look at some differences between English as spoken on both sides of the Atlantic.
Holiday Inn UK - I Say Tomato: American-British travel dictionary and a few dozen British to American translations.
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.
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.
United Kingdom English for the American Novice: Words and phrases that may cause problems for American visitors.
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.