Learn something new — because boredom is wasted potential

"Personality and logic quizzes"

1. 1.
   16 Personalities
2. 2.
   Human Benchmark

"Cognitive exercise games"

1. 1.
   Lumosity
2. 2.
   Brilliant
3. 3.
   Sudoku.com
4. 4.
   Chess.com
5. 5.
   Lichess

"Contribute to real science"

1. 1.
   Zooniverse
2. 2.
   Foldit (Protein Game)
3. 3.
   SETI@home

"Open courseware & skills"

1. 1.
   Open Culture
2. 2.
   Coursera
3. 3.
   Khan Academy
4. 4.
   MIT OpenCourseWare
5. 5.
   Wolfram MathWorld
6. 6.
   TED-Ed
7. 7.
   Codecademy
8. 8.
   freeCodeCamp
9. 9.
   Duolingo
10. 10.
    Memrise
11. 11.
    Forvo (Pronunciation)
12. 12.
    DOAJ (Open Journals)
13. 13.
    JSTOR Open Content
14. 14.
    Google Scholar
15. 15.
    ResearchGate

"Creative coding challenges"

1. 1.
   CodePen Sparks
2. 2.
   Shadertoy
3. 3.
   Codewars
4. 4.
   CSS Zen Garden
5. 5.
   Can I Use (Tech)
6. 6.
   Hackaday
7. 7.
   Arduino

"Interactive geometry/math"

1. 1.
   Desmos Graphing
2. 2.
   Wolfram Alpha
3. 3.
   GeoGebra
4. 4.
   Math Is Fun

"Vocabulary and immersion"

1. 1.
   Babbel Magazine
2. 2.
   italki
3. 3.
   AnkiWeb

"Competitive programming sites"

1. 1.
   LeetCode
2. 2.
   HackerRank
3. 3.
   Codeforces
4. 4.
   Exercism
5. 5.
   Project Euler
6. 6.
   Topcoder
7. 7.
   CyberChef

"Aesthetics typing games"

1. 1.
   Monkeytype
2. 2.
   Typeracer
3. 3.
   Keybr

"Cooking theory and recipes"

1. 1.
   Serious Eats
2. 2.
   Bon Appétit
3. 3.
   Allrecipes

"Grammar and style helpers"

1. 1.
   Hemingway Editor
2. 2.
   Thesaurus.com
3. 3.
   RhymeZone
4. 4.
   OneLook Dictionary
5. 5.
   LetterPile
6. 6.
   Scrivener
7. 7.
   Archive of Our Own

"Number theory databases"

1. 1.
   OEIS (Integer Sequences)
2. 2.
   Wolfram MathWorld
3. 3.
   Numberphile