We tend to think of learning a new skill or "going back to school" as something you'd do when looking to change careers, or to upgrade within your current one.

But lifelong learning has incredible benefits, both personal and professional, say researchers. It makes communities more productive and innovative, and gives employees the ability to cope with constantly changing workplaces. Lifelong learning helps us stay sharp as we age, and is also important for a successful economy.

It helps us communicate better, socialize more effectively, and achieve greater success.

Whether you're looking to learn how to code, build leadership skills, or otherwise improve yourself, here are 27 awesome places to learn the critical skills that will change your life:

1. Lifehacker

One of my favorite sites on the planet, Lifehacker is the place to learn how to do just about anything better, faster, and smarter.

2. Library of Congress

Most of our national library's texts are now available online. Whatever skill it is you want to learn, you can read up on it there.

3. Boundless

Remember taking on a second part-time job just to pay for your college textbooks? Boundless is shaking up the textbook industry by offering textbooks online, for free.

4. Inc.edu

Inc.'s own educational site is an amazing resource for entrepreneurs looking to build the skills most likely to help them succeed. These real-time, live workshops led by all-star entrepreneurs are the best way to cut the learning curve and connect with people who really have the experience to lead by example.

5. Universities

Most universities now offer online learning courses in addition to the on-campus lifelong learning programs. Some have established entire online schools, like Colorado State's Osher Lifelong Learning Institute. If you're looking for a more traditional educational experience, check out what the universities are offering.

6. Google World Wonders

Explore the ancient and modern worlds in an incredible online resource powered by Google's Street View and mapping technology.

7. TED Talks

TED is another fantastic place to find actionable advice and learning opportunities created by genuine, experienced people. I've curated my favorite TED Talks for entrepreneurs, leadership training and creativity in business -- check them out for yourself. You can also visit TED Ed for its own selection of great lessons.

8. Reddit Lectures

This crowdsourced collection of top lectures from professionals, academia, governments, and leaders of all stripes is unique in that the resources are upvoted or downvoted by users, in typical Reddit fashion.

9. UReddit

Speaking of Reddit, the forum site has its own University of Reddit, with dozens of courses in the arts, computer science, language, math and statistics, and more.

10. Internet Sacred Text Archive

It's the largest archive of free books on religion and spirituality on the internet. Read up on mythology, religion, folklore, alchemy, parapsychology, and more.

11. MeetUp

See what's happening in your area and meet up with like minds to learn new skills, often free of charge. Meetups are a great way to trade experiences and learn new perspectives.

12. Trivium Education

Critical thinking is an incredibly important skill, but it's not often taught in public school curriculum. Brush up on your rhetoric, grammar, and logic with Trivium's free resources.

13. HubSpot Academy

HubSpot, that online marketing software giant out of Boston, offers comprehensive, user-friendly digital marketing courses. Understanding marketing is critical for any entrepreneur, whether it's a function of your daily duties or not. HubSpot Academy was one of my own top five digital marketing course picks.

14. University of the People

Billing itself as the world's first non-profit, tuition-free, accredited, online American university, UoPEOPLE offers degree programs in Business Administration, Computer Science and Health Studies.

15. PBS Video

Watch well-researched, in-depth documentaries from PBS, free of charge online.

16. Project Gutenberg

Study classic literature for free with over 50,000 titles available to download from the Project Gutenberg library.

17. Pocket

Save articles, videos and other interesting and educational content you come across online to consume later. Pocket lets you save from your browser, or from apps like Twitter or Flipboard, and you can access the content later without an internet connection.

18. MIT Open Courseware

The iconic university offers totally free programming courses, including an introduction to computer programming course that's fantastic for entrepreneurs and beginners. It was my top choice among the nine best places to learn how to code for free.

19. iCONIC Tour

Inc.com and CNBC put together iCONIC, a three-part conference series that's visiting my own hometown of Boston on September 22, 2016, after its first stops in Seattle and Denver. On top of the excellent speakers, the networking is an incredibly effective way to learn what's truly working for dynamic businesses across the country.

20. FutureLearn

Packed with free online courses from over 40 universities, FutureLearn is a U.K. site that serves over 3.6 million learners worldwide.

21. Rescue Time

Learn more about where and how you spend your time, allowing you to find efficiency throughout the day.