1) Etomyonline - Etymological Dictionary
See the origin of words and the way in which their meanings have changed throughout history. Keep your language of its time with this site and the next:
2) Google ngrams - frequencies of short sentences found in sources printed between 1800 and 2012
3) Behind the name - etymology of first names
Very useful when used in conjunction with the next site:
4) Fake Name Generator - not just names but biographies
Ideal when you're stuck for background characters. Characters like
Amanda Castro Carvalho. Born and raised in Switzerland of Brazillian parents. She was born on October 19, 1987, making her 27 years old and a Libra
Was £20 a week a good wage back in 1960? How much would Mr Darcy's 10000 a year be in today's money? The Bank's Inflation Calculator shows how the cost of goods and services changes over time as prices change. You can check the effect of price changes over any period from 1750 to 2013.
Unlike search engines, which merely return documents, Wolfram Alpha tries to work out answers from questions. To get an idea of how Wolfram Alpha differs from Google, say, try asking them both how far away the moon is, then compare the answers.