khanacademy.org – Watch thousands of micro-lectures on topics ranging from history and medicine to chemistry and computer science.
freerice.com – Help end world hunger by correctly answering multiple-choice quizzes on a wide variety of subjects.
Inktank.fi – Awesome and awe inspiring articles all in one wonderful place.
artofmanliness.com – Blog/site dedicated to all things manly, great for learning life skills and good insights.
unplugthetv.com – Randomly selects an educational video for you to watch.
coursera.org – Educational site that works with universities to get their courses on the Internet, free for you to use.
conversations.nokia.com – Learn about the world’s most innovative smartphones and future mobile tech.
lizardpoint.com – A collection of browser-based games and the like to improve knowledge of geography, math, and such.
ted.com – Collection of TED (Technology, Entertainment and Design) talks in which knowledgeable speakers address a variety of topics in short videos (< 18 minutes)
lifehacker.com – Learn to hack life! Tips and tricks for improving all areas of your life.
lifehackninja.com – Recently started life hack site that offers lists of useful knowledge
good.is/infographics – Collection of infographics which showcase useful information in an easy to digest visual format.
mathrun.net – Practice your basic maths skills with a simple game.
Litro.co.uk – All you need to know about the wonderful world of books and writing.
justinguitar.com – Hundreds of free guitar lessons as well as some basic music theory.
duolingo.com – Learn a new language for free while helping to translate the web.
memrise.com – Learn things quickly and efficiently with flashcards that are spaced based on the spacing effect
cookingforengineers.com – A site containing one man’s explorations in food, with step by step instructions for making a wide variety of dishes.
thedatingspecialist.com – A weekly blog run by a professional dating coach, offers advice on a wide variety of relationship topics.
zenhabits.net – Blog about improving your life by making it simpler.
nerdfitness.com – Fitness resource for the average person.
mentalfloss.com – Interesting articles guaranteed to make you smile and get you thinking.
openculture.com – Compendium of free learning resources, including courses, textbooks, and videos/films.
charitynavigator.org – Site dedicated to reviewing charities so you can easily research any you’re interested in.
lettersofnote.com – Their tagline says it all: “Correspondence deserving of a wider audience”
thedailymiscellany.com – A daily dose of useful knowledge, quotes, and other random things.
MIT Open Courseware – Free access to quite a few MIT courses that are on par with what you’d expect from MIT.
codecademy.com – Website packed with introductory courses for various programming languages and web technologies.
investopedia.com – Learn about the world of finance, from basic terminology to in depth analysis of various areas of investing.
udacity.com – Free courses mainly focused around mathematics and programming. Aimed at people of all skill levels.
lang-8.com – Write posts in a language you’re trying to learn, get them critiqued by a native speaker (and in turn help that native speaker learn your language)!
careerbuilder.com – Job hunting site to help you find a new career.
ureddit.com – Reddit’s very own University. Learn from redditors, or try to teach them.
engineerguy.com – Collection of videos in which Bill breaks down various feats of engineering in layman’s terms.
zooniverse.org – Take part in a huge variety of interesting studies of nature, science, and culture.
quora.com – Ask questions you’re curious about, answer those you’re knowledgeable about. Tailor your own feed to fit what interests you.
thenewboston.org – A fascinating collection of videos and tutorials related to maths and computer science.
aldaily.com – Aggregation of articles from various higher education journals and publications.
noexcuselist.com/everything – A huge list of awesome sites to learn from.
livemocha.com – Community dedicated to the idea of everyone being fluent in multiple languages, teach or be taught another language with the goal of conversational fluency.
simplesciencefitness.com – Breaks down the science behind fitness into layman’s terms.