Project Gutenberg - Free books
OpenLibrary - download out-of-copyright books, borrow in-copyright books
LibriVox - Free audio books
Podiobooks.com - free audiobooks mostly from self-published authors.
Documentary Heaven - Free documentaries
TopDocumentaryFilms.com and FreeDocumentary.tv - more free documentaries.
Last.fm - Keeps track of your listening habits
Songza - Playlists for whatever mood you're in.
8tracks - Another playlist service with playlists created by users. Internet radio created by people, not algorithms.
Popcorn Time - /r/PopCornTime
Media Hint - Allows for US Netflix and Pandora access for those of us living abroad. Turns out Media Hint are now charging but here is a workaround
ZenMate - (Chrome extension) MediaHint alternative.
Hola Unblocker - Same as above, allows access to US Netflix, Hulu, Pandora, etc. but be warned.
Soundozer - it's kind of like Pandora, but you can listen to any song you search for and you can create a station based on that song. You don't have to register either.
Grooveshark - free music, online radio, streaming. recommended by /u/freebytes
Jango - Free music - internet radio that plays what you want, great for those who can't access Pandora. recommended by /u/your_mind_aches
Pornhub - free porn, nuff said
TBLOP - The big list of porn
Thumbzilla - more porn.
That Mp3 - Convert YouTube to Mp3. Really simple. Don't click on any ads.
Courses and tutorials:
Class Central - Discover free online classes (MOOCs) from top universities like Stanford, MIT, Harvard, etc.
Open2Study - recommended by /u/SpiceFox
FutureLearn - Learning for life, provided by UK and international universities. recommended by /u/fdsafdaw3f3acvsda
iTunes U - iTunes University offers many free open courses from leading university. recommended by /u/wuisawesome
Harvard Open Courseware
MIT Open Courseware
Yale Open Courseware - actual video lectures for the class so you can get the in-class experience. Lots of classes over lots of subjects.
Stanford Open Courseware
EDX - Free courses from the best universities, you can even get a diploma for a few dollars. recommended by /u/Ghune
Khan Academy - Free learning tutorials on just about every subject.
PatrickJMT - making FREE and hopefully useful math videos for the world! recommended by /u/thejoce1
Codecademy Free interactive coding tutorials
Become a programmer, motherfucker
Duolingo and FSI Language courses- Free language learning
Memrise - Learn vocabulary, languages, history, science, trivia and just about anything else easily using flashcard techniques. Recommended by /u/exploiting
Anki - Similar to Memrise. Anki is a program which makes remembering things easily. Intelligent flashcards
Ted Talks - Free talks and lecture about anything and everything
Wolfram Alpha - Your one stop shop for calculations and questions about anything
Mathway - Awesome math problem solver. recommended by /u/RedS94
A giant collection of Computer Science books made freely available
FreeRice - Answer vocabulary questions and rice is donated to charity! /u/Jowzer 's recommendation. Be sure to turn off adblock when using this site, as that's how they supply the rice! (Thanks for the heads up /u/Jack0fspad3s)
Mendeley - The best free way to manage your research. Organize, share, discover. Great for when writing a paper, it manages all your referencing/bibliography in many different available notations
7 Cups of Tea - Free, anonymous, and confidential conversations with trained active listeners. Please don't spam the site, they offer a great service
Thrive On - Not completely free, but aims to bring affordable online mental health programs to those who would otherwise go without. Starting next month
Blah Therapy - Online listening service. "Experience the rewards of venting to a stranger or lending an ear."
MoodGYM - Learn cognitive behaviour therapy skills
for preventing and coping with depression. recommended by /u/sunnysidemegg
Social Services resources - a subreddit created by a professional Social Worker who has spent a career procuring resources for those in need. /u/TheFightGoes0n
Ninite - update/install all your programs at once
PortableApps - load several apps on a thumb drive to run on any Windows PC. recommended by /u/danteas1
SlimDrivers - Cloud based program that detects what drivers need to be updated. Incredible--especially after formatting an operating system. No need for CDs or trying to remember which model card, adapter...etc. you have.
Copy - Online cloud storage. Start with 15gb free. Or 20gb with a referral link.
BitTorrent Sync - Secure, unlimited file-syncing. No cloud required
SyncThing - opensource alternative for bitsync. its recommended if you care about your privacy and security of your files. recommended by /u/akeryw
Mega Desktop Sync(50GB) and Symform (Unlimited, but you must share back!) - both cloud storage services recommended by /u/muntoo
Calibre - Free ebook library management
F.lux - Adjusts the gamma on your screen uses magic as the day progresses to reduce eye strain.
GIMP - Free photo manipulation software
Inkscape - Free and open vector graphics editor.
Paint.NET - Windows application designed to be the much needed upgrade to MS Paint. recommended by /u/SquirreI and /u/zeaga
Pixlr - Online photo editor. web-based equivalent to an old version of Photoshop from 2005 or something. Very functional for occasional use manipulating images, and seeing as it's web-based and doesn't require an account it's super easy to use from anywhere. recommended by /u/abercromby3
Sumo Paint - Powerful graphics editor for your web browser and pc, recommended by /u/NotMyCircus
Blender - Open source, cross platform suite of tools for 3D creation. recommended by /u/Tom7980
Prey Project - Multi-platform anti-theft software
RES - Reddit enhancement suite - A must have for all you redditing needs
KeePass - free, open source, light-weight and easy-to-use password manager.
LastPass - free (with premium for multiple platforms), easy-to-use password manager.
Dictionary Pop-up extension, double click on a word that you don't know the meaning of and a dictionary definition pops up. Firefox extension powered by dictionary.com. Chrome extension powered by Google
ClipCube - clipboard history.
ClipX - ClipX is a tiny clipboard history manager. It is sweet, it is free, use it. ClipCube alternative.
LeechBlock (Firefox add-on) - simple productivity tool designed to block those time-wasting sites that can suck the life out of your working day. recommended by /u/Rae_Starr
StayFocused - Chrome alternative to LeechBlock, recommended by /u/Jeskid14
Reaper - Audio workstation. Not free. Just a trial.