This comment from /u/SaidinWoT was extremely helpful in allowing me to find webs
ites to use that aren't wasteful:
khanacademy.org - Watch thousands of micro-lectures on topics ranging from histo
ry and medicine to chemistry and computer science!
freerice.com - Help end world hunger by correctly answering multiple-choice quiz
zes on a wide variety of subjects!
fuckinghomepage.com - LINKS TO FUCKING AWESOME SHIT THAT CHANGE EVERY MOTHERFUCK
artofmanliness.com - Blog/site dedicated to all things manly, great for learning
life skills and good insights.
unplugthetv.com - Randomly selects an educational video to watch instead of usel
coursera.org - Educational site that works with universities to get their course
s on the internet, free for you to use!
lizardpoint.com - A collection of browser-based games and the like to improve kn
owledge of geography, math, and such.
ted.com - Collection of TED (Technology, Entertainment and Design) talks in whic
h knowledgable speakers address a variety of topics in short videos (< 18 minute
lifehacker.com - Learn to hack life! Tips and tricks for improving all areas of
lifehackninja.com - Recently started life hack site that offers lists of useful
good.is/infographics - (Note: /u/gerbalgerbal typo'd to /inforgraphics, which do
es exist but isn't much of anything) Collection of infographics to get some good
information in an easy to digest visual format.
mathrun.net - Practice your basic math skills with a simple game
justinguitar.com - Hundreds of free guitar lessons as well as some basic music t
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 spac
ed 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, offe
rs 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 - Articles meant to expose you to interesting info, whether to "
make you smile" or to really get you thinking.
openculture.com - Compendium of free learning resources, including courses, text
books, and videos/films.
charitynavigator.org - Site dedicated to reviewing charities so you can easily r
esearch any you might be interested in and see how they hold up.
lettersofnote.com - Their tagline does better than I can: "Correspondence deserv
ing of a wider audience"
thedailymiscellany.com - On the opposite end of the vulgarity spectrum from fuck
inghomepage.com, a daily dose of useful knowledge, quotes, and other random thin
Adding in some suggestions from elsewhere in the thread (sorry if I missed any):
MIT Open Courseware - Free access to quite a few MIT courses that are on par wit
h what you'd expect from MIT. (from /u/1900david)
codecademy.com - Pretty nice website with introductory courses for various progr
amming languages and web technologies. (from /u/Archaya (and others, Archaya jus
t replied directly to this post))
investopedia.com - Learn about the world of finance, from basic terminology to i
n depth analysis of various areas of investing. (from /u/IAmNotAPerson6)
udacity.com - Free courses mainly focused around mathematics and programming. Ai
med at people of all skill levels, redditors really seem to like it (I've never
actually tried it). (from /u/veggie124 (and possibly others))
lang-8.com - Write posts in a language you're trying to learn, get them critique
d by a native speaker (and in turn help that native speaker learn your language)
! (from /u/smallpoly)
careerbuilder.com - Job hunting site meant to help you find a career. Rather apt
ly named. (from /u/NOT_ACTUALLYRELEVANT)
ureddit.com - Reddit's very own University! Learn from fellow redditors, or try
to teach them. (from /u/Gr1pp717)
engineerguy.com - Collection of videos in which Bill breaks down various feats o
f engineering in layman's terms. (from /u/Bovisaurus)
zooniverse.org - Take part in investigating various interesting studies of natur
e, science, and culture. (from /u/velawesomeraptors)
quora.com - Ask questions you're curious about, answer those you're knowledgable
about. Tailor your own feed to fit what interests you. (from /u/virjog)
aldaily.com - Aggregation of articles from various higher education journals and
publications. (from /u/Hesprit)
noexcuselist.com/everything - A convenient list of lots of awesome sites to lear
n from. Includes pretty much everything listed here, helpfully grouped into cate
gories. Hover over links to get descriptions that may or may not beat out mine!
livemocha.com - Community dedicated to the idea of everyone being fluent in mult
iple languages, teach or be taught another language with the goal of conversatio
nal fluency. (from /u/bearfiesta)
simplesciencefitness.com - Breaking down the science behind fitness into layman'
s terms. (from /u/lapiak)