AskOxford.com is a website produced by the publishing house Oxford University Press (OUP), a department of the University of Oxford in the United Kingdom. OUP is also the publisher of the Oxford English Dictionary, among other things.
The site is largely dedicated to selling OUP's books but does offer good free help on use of the English language, including spelling, grammar and writing tips, as well as access to the Compact Oxford English Dictionary. It also has information on learning foreign languages, etymology - history of words and usage of words, teaching resources for schools, competitions to win books, a large Frequently Asked Questions section ("Ask an Expert") and the option to email or contact by mail the Oxford Word and Language Service (OWLS) ("Contact Us") who answer questions not covered in the FAQs about the English language for free.
It also has a commercial "shop" section, which largely consists of selling dictionaries and other related material published by OUP.