5 reasons to try Vocabulary.com

• Vocabulary.com does a great job of "gamify-ing" the process of building your vocabulary through its adaptive learning system
• It is among the PC Magazine's Top 100 Websites & the Time magazine's top 50 websites of 2012 
• The site's main attraction, the quiz, has some 100,000+ questions and the answers are educative. The site reportedly contains over 100 million sentence examples.
• The site is ad free
• Their dictionary is blazing fast. In an unscientific comparison, it seemed to beat another contender, thefreedictionary.com with the print layout, for the title of world's fastest, smartest dictionary. 

While there is no mention on the current version of the website about who created it and when, going by the records on Archive.org it appears to have started in 1998 by the husband-wife team of Jan and Carey Cook. The gamification of the site seems to have been done around the April 2011 period.

I learnt about the site from the English.SE Q & A website and I'm hooked. I have a few nits to pick though.

The way the scoreboard sticks to the quiz section, it seems there is something hidden below the quiz box. A small left margin for the scoreboard would make it a less distracting for me. 

A keyboard shortcut to move to the next question would be nice.

Also see:

Wordament - Tips, Tricks & Trivia

WordWeb - the desktop English teacher