MOST PRODUCTIVE WAY SPENDING TIME ON INTERNET

Let start the topic.
1st one - where you are reading my blog i.e. STEEMIT

2nd one we know we are spending lots of time in you tube.
It is bighest platform.

  New additions to Youtube Channels you can follow:

1-TED-Ed (Highly Recommended): TED-Ed’s commitment to creating lessons worth sharing is an extension of TED’s mission of spreading great ideas. Within TED-Ed’s growing library of lessons, you will find carefully curated educational videos, many of which represent collaborations between talented educators and animators nominated through the TED-Ed platform.
(2)-Shots of Awe (Highly Recommended) - Jason Silva (the host of Brain Games) will certainly blow your mind!
thenewboston (Recommended): You will learn (3)-more by watching Bucky Roberts teach you stuff than by spending time anywhere else. From Photoshop to Python to C++ to Java to Adobe Effects - you name it!
(4)-How to start a startup: Everything about how to start a startup, for free, from some of the world experts. The series of lectures offer close to 1,000 minutes of content if you watch it all.

Additions to Websites and Blogs you can follow:

(1)-Spirit Science: Everything related to existence, life, spirituality and more.
The Next Web: One of the best sources for technology and business related news. They have quite an active Youtube channel as well which is worth checking out.
2-Gibbon: Gibbon is an amazing source of curated knowledge from an inspiring community. It offers what they call as "playlists for learning" wherein you get to learn things via articles, videos and more - all in step by step manner.
(3)-Oliver Emberton: Oliver is an inspiring writer. He is like those teachers who break a hard to understand concept of life into an example that will stay with you for a long time. I am a regular reader of his blog and I can vouch for the quality and effectiveness of his writing. Bonus: You can also follow him on Quora: Oliver Emberton.
(4)-8tracks (Highly Recommended): Go nowhere else for great music on the internet!
(5)-Digital Inspiration: Mr. Amit Agarwal authors the hugely popular and award-winning Digital Inspiration blog where he writes how-to guides around computer software, consumer gadgets, and web apps. You will be surprised by how much you can learn by just following his blog weekly!
(6)-Less Wrong: A community blog that will make you question yourself, your life and your existence as a whole - offering you a more rational perspective on the whole. Ex article: Simulate and Defer To More Rational Selves

(7)-HubSpot Blog (Recommended): If you are a business professional (especially a Marketer) then you should not miss Hubspot at all. It's famous for its amazing and quality content on everything. Ex article: Psychology for Marketers: 9 Revealing Principles of Human Behavior.

(8)-Buffer blog: Everything related to social media. They offer creative content and will never bore you with their articles. Even if you are not a social media professional, you will end up loving some of their articles. Ex article: 15 Psychological Studies That Will Boost Your Marketing.

(9)Medium : An amazing place to blog (I love their design) and be a part of a growing community of storytellers from around the world.
Original Answer
There are numerous websites, blogs, Youtube channels etc out there for you to make the most of your time when wired in.

Here's a list of some blogs and websites that you can follow:
Brain Pickings (Highly recommended)- Brain Pickings is a human-powered discovery engine for interestingness, a subjective lens on what matters in the world and why, bringing you things you didn’t know you were interested in — until you are. It is maintained by Maria Popova who reads over 12-13 books a week to post all the awesomeness that's in there.
HowStuffWorks (HighlyRecommended) - HowStuffWorks is a wholly owned subsidiary of Discovery Communications and is the award-winning source of credible, unbiased, and easy-to-understand explanations of how the world actually works. Gamut of categories to feed your intellectual hunger.
TED: Ideas worth spreading - Learn from the experts by watching under 20 minutes of mind expanding talks. Start with Sir Ken Robinson's talk:-How schools kill creativity!
Investopedia- Learn everything there is to know about finance. From dictionary to tutorials, they have it all!
Mind Tools - An amazing website to train you in different aspects of life!
Mental Floss - An amazing website that offers random, interesting articles and facts.
The Art of Manliness - Another mind expanding blog to keep you inspired and intellectually hungry. Example article The Power of Ritual: Building Shared Worlds and Bonds That Transcend the Everyday
BBC - Future - Know more about the future stuff that matters. Example:Timeline of the far future
Litemind .(Recommended) - Litemind is about exploring ways to use our minds efficiently. Covering articles on being more creative,thinking more clearly, boosting your brainpower, developing yourself and more.
Entrepreneur. - For all the entrepreneurs out there.The website offers some amazing insights related to entrepreneurial world.
Stumbleupon (Recommended) : This helps in discovering more stuff that interests you!
Big Think: They have some great stuff!
The Mind Unleashed: Helps you discover yourself scientifically, culturally and intellectually. Example article: What If Everything You Were Ever Taught Was A Lie?
Top Documentary Films - - Choose from a wide category and watch some interesting documentaries. Example (and favorite one): The Century of the Self (Highly recommended)
Free Online Course Materials (MIT OpenCourseWare), Coursera,edX - They need no introduction!
Project Gutenberg - Find over 40,000 ebooks
Goodreads - Learn more about your favorite books, review them, find lists, award winning books, quotes, trivia, join reading groups etc.
Zenpecils - Meet art + inspiration + mind expansion.
MAKE- DIY Projects, how-tos and inspiration from geeks, makers and hackers.
Duolingo (Highly Recommended): Want to learn a new language but can't find a reliable source? Duolingo is your solution.
The Muse: For some kick-ass career advice and more!
Coffitivity - Did you know that cafes are one of the best places to spark your creativity? Since now you do, check out coffitivity that creates the atmosphere of a coffee shop straight from your laptop/PC.
IFTT: Standing for “if this then that,” IFTTT helps different apps, online programs, and services work together to make your life way easier. Think getting the weather texted to you every morning or having your photos automatically save to Dropbox. :D
Codeacademy (Highly Recommended): Extremely addictive website that helps you make the most of your time on the internet and teaches you all about the languages that back it and more!
Canva: Love designing? Then here's Canva for you that makes designing insanely easy for you and the only limitation is your imagination.
Sporcle: Sporcle is still the best place on the internet for testing your knowledge. You can take quizzes on any topic imaginable, which is a pretty fun way to learn new things (and also to challenge your co-workers to see who knows more about obscure TV references or countries of the world).
FACTSlides → Amazing FACTS you didn't know!: FACTSlides allows you to click through a variety of random facts that not only feed your curiosity, but are also perfect fodder for the break room. For example, did you know that UPS delivery trucks save 10 million gallons of gas every year by making no left turns?
99U : An amazing blog that keeps your brain healthy by stimulating it with beautiful insights into creativity and more!
Fast Company (Highly Recommended): You will never get bored of FastCo if you love business, innovation and everything in between.
zenhabits: One of the most popular blogs out there. Leo's advice on life and his thoughts about stuff we take for granted is marked by extremely meticulous and perspicuous insights.
Farnam Street: Recently discovered this gem of a blog. From Psychology, to books, to decision making, one can find very interesting reads on the blog.
Now some Youtube channels that you can

follow!
Veritasium
Vsauce (Highly Recommended)
MinutePhysics
Numberphile
SciShow
AsapSCIENCE(Highly Recommended)
The RSA
Big Think (Recommended)
eHow (Recommended)
SmarterEveryDay
Last but not the least, for some mind expanding documentaries (Over 300 + of them) check Down The Rabbit Hole We Go! 300+ Mind Expanding Documentaries

I hope this helps. :)