The Web is fast replacing reference books. References to almost any information can be found online quickly. In fact, it is often faster to look up information online than to look in a book already on your bookshelf. Of course, an online lookup is also much cheaper than purchasing a reference book.
Here are some reference sites that I have found to be useful to genealogists:
A List of Occupations, many of which are archaic: http://www.rootsweb.ancestry.com/~usgwkidz/oldjobs.htm.
Archaic Medical Terms: Rudy’s List of Archaic Medical Terms at http://www.antiquusmorbus.com/, Cyndi’s List of Medical Terms at http://www.cyndislist.com/medical#Diseases, a list of archaic medical terms and meanings used in various English speaking countries at http://www.genproxy.co.uk/old_medical_terms.htm, and theEncyclopedia of Genealogy at http://www.eogen.com.
The Getty Thesaurus of Geographic Names: http://www.getty.edu/research/tools/vocabulary/tgn/index.html
The Geographic Names Information System (GNIS), developed by the U.S. Geological Survey in cooperation with the U.S. Board on Geographic Names (BGN), contains information about almost 2 million physical and cultural geographic features in the United States: http://geonames.usgs.gov/index.html
Glossar: Die Familie: English-German glossary of terms frequently found in genealogy research: http://www.univie.ac.at/voelkerkunde/cometh/glossar/heirat/h-menu.htm
Meanings and origins of first names – an etymology (the origin of words) and list of the most popular names: http://www.behindthename.com/
Cemetery Junction Directory – A directory of more than 50,000 cemeteries. Search by cemetery and family name. Links to obituaries and genealogical societies in the U.S, Australia, and Canada: http://daddezio.com/cemetery/
A Glossary Of Terms Used In Heraldry (coats of arms): https://www.heraldsnet.org/saitou/parker/index.htm
Where to Write for Vital Records – Addresses and guidelines for contacting each U.S. state or territory for vital records and documents: http://www.cdc.gov/nchs/howto/w2w/w2welcom.htm
There are many, many more such lists online. You should be able to find them with any search engine. However, the above is a list of the ones I keep handy. If you have others that you like, post them to the end of this article at and I will update the list.