1. Is My Computer On?: http://www.ismycomputeron.com/
You need to check before you go into the next DONGs.
2. CodeCademy: https://www.codecademy.com/
Here you can learn about coding in HTML5, CSS, Javascript and more for free.
3. PTable: http://www.ptable.com/
Learn about the elements in the periodic table just by clicking on it.
4. Historia Civilis: https://www.youtube.com/channel/UCv_vLHiWVBh_FR9vbeuiY-A
A YouTube channel dedicated to talking about the history and tactics of war like the Roman Army.
5. Crowd Haiku: http://www.crowdhaiku.com/
Submit what words you want, and it'll generate a Haiku which you can vote on.
6. The Obsessively Detailed Map Of American Literature's Most Epic Road Trips: http://www.atlasobscura.com/articles/the-obsessively-detailed-map-of-american-literatures-most-epic-road-trips
It shows the paths taken in different books so you can plan your own trip.
7. Just Park: https://www.justpark.com/creative/is-it-illegal/
A color-coded website which shows you the laws that apply for driving in different states.
8. Solar System Visualizer: http://janus.astro.umd.edu/SolarSystems/
...
9. World Without Us: http://www.worldwithoutus.com/did_you_know.html
An infographic that chronicles what would happen on earth following the first 5 billion years after we're gone.
10. 30 GB of 80’s/90’s Music: https://archive.org/details/noise-arch
Discover 30GB of underground music from the 80's and 90's.
11. Public Domain 4U: http://publicdomain4u.com/
It's dedicated to preserving and providing a home for a collective musical heritage.
12. Drawings Of Leonardo: http://www.drawingsofleonardo.org/
It lets you take a close look at the sketches of Leo, no, not DiCaprio.
13. I Write Like: http://iwl.me/
You write any kind of text and the site will tell you the writer you write more similar to.
14. Barcode Art: http://www.barcodeart.com/art/yourself/yourself.htm
Just enter basic information about yourself and the website will create a personal barcode for you like Agent 47.
15. Foggy Shores: https://ocias.com/games/foggy-shore/index.php
A meditative game that takes place along a misty beach.