Need an appropriate exclamation for your hero?  Check out my list of Expressions.  There you’ll find the ones most commonly used during the Regency period, and when each first showed up in the language. 

If you're searching for slang spoken by criminals, waterfront rogues and similar low life, check out Cant, my abridged version of the 1811 Dictionary of the Vulgar Tongue.  I've organized select words by topic, then alphabetically.

Under Articles can be found several nonfiction pieces I've written on topics that may be of some interest.  They include one on women assuming male roles during 18th & 19th centuries; a history of Minerva Press; burial practices and religious attitudes about suicides; information about Gretna Green.  In addition, you'll find a list of body language cues to emotion, and color terms under Craft. 

Here are some websites I've found very useful:

1662 Book of Common Prayer  
British History Online-- The definitive source for information about everything from the architecture of Almacks to specific political figures.   
British Titles List  -- Wikipedia list of extant and extinct titles dating from 1066-present. Includes the family name.
Book of Household Management by Isabella Beeton-- Late 19th century, but chock full of advice on how to deal with servants and other household issues.  Wonderful period recipes, as well as priceless info on what to do with rancid butter, etc...
Calendar-- Need to know what day Christmas fell on in 1814?  The phase of the moon for a specific date in history?  Check out this site.  It can generate calendars for any year and any country. 
Climate History-- mean temperatures in Central England from 1659 to present.  Figures are in celsius.
Even More Climate History-- rainfall in England and Wales from 1914 to present.  Figures are in millimeters.  Monthly minimum and maximums are calculated.
Consanguinity -- a table of marital relationships forbidden by the Church of England.
Decoration of Houses by Edith Wharton-- Written in the late 19th century.  Wonderful descriptions of walls and window treatments, floors and ceilings, halls, ballrooms and saloons.  Trying to figure out what furniture is in your heroine's bedchamber?  This is the place.
Domestic Medicine in 1785 by W. Buchan
19th Century Women and the Monthly Cycle -- by Virginia Mescher.  How women coped.
Gaskell's Compendium of Forms-- Late 19th century but sure to be applicable earlier.  Written form of address for letters of condolence and apology, dinner invitations, weddings and balls.
Great North Road -- history and construction of, geology, maps, distances between towns.
Horse/Traveling Facts -- Jean Ross Ewing/Julia Ross' excellent resource on the care and feeding of horses, plus how far they can travel.
How Much Is That? -- Calculate how much today’s dollar or pound was worth in a specific year.
Inns of Old London -- alphabetical resource of information on the inns of London and other information on historic buildings in Britain.
Internation Dialects of English Archive -- hear different British accents.
Introduction to the House of Lords Ceremony --detailed account of the ceremony.  It was changed based on the recommendations in this 1998 report.
Leigh's 1819 New Picture London -- everything the Regency writer needs to know about life in London.  From how provisions were supplied, to street indexes, places of worship and public buildings.
Letters from the Past -- provided by the Victorian Web.  Information about postage costs during the Regency period, franking and who paid what.  Many fine examples of period letters.
London Panoramas -- 360 degree views of select bridges, squares, parks, etc...
Making Fire with Flint and Steel -- the procedure for lighting fires in the days before Lucifer sticks.
1792-9 Map of London
Cary's 1818 Map of London
1827 Map of London
1859 Map of London  
Names of the Regency Period -- Kat Inkslinger's spreadsheet of popular names in Regency England.
Nature Online -- from the Natural History Museum in London.  English and Scottish flora and Fauna types by postal code.  Plant, animal, and insects.
Parliament/Legislation of the United Kingdom -- Wikipedia list of legislation from 1601-present day.  Not complete.
Peerage -- everything a writer needs to know about the peerage system in Britain.  Note:  this is a modern point-of-view so some policies have changed.
Prices and Wages 1700-1725 
Proceedings of the Old Bailey -- contains accounts of 100,000 criminal trials 1674-1834
Provincial Glossary -- by Francis Grose, author of the Dictionary of the Vulgar Tongue.  Includes local proverbs and superstitions.
Regency Dancing -- everything you want to know about the topic, including dance steps.
Regency Skin Care & Cosmetics -- Yvonne Forsling's excellent website on the topic.
Regency Homes -- Gaelen Foley's marvelous resource on the layout and structure of Regency townhomes.  Complete with photos. 
Smugglers' Britain --the unedited online version of Richard Platt's excellent resource.
Squares of London -- Georgian Index's outstanding site for descriptions of and tenants living in London's residential squares during the Regency.
Vauxhall Gardens -- singers, musicians, performers, proprietors and staff from 1661-1859
Views of London -- views of buildings and squares