1. Nulling The Void: http://www.nullingthevoid.com/

Animation of rocks or meteorites falling and exploding.
2. I Will Knot: http://www.iwillknot.com/

This website teaches you all about knots.
3. Planet Families: http://www.alienearths.org/online/interactives/planet_families/index.php

Here you can create your own solar system, place the planets wherever you want and watch them interact. Similar to previous DONGs.
4. Earth Editor: http://dan-ball.jp/en/javagame/ee/

Create your own planet, you are given various materials to build it, you can even use fire.
5. Are You A Replicant?: http://www.bfi.org.uk/are-you-a-replicant/

A test from the Blade Runner universe to prove if you're a real human or a synthetic one.
6. Spurious Correlations: http://tylervigen.com/spurious-correlations

A website that that shows graphs that show weird correlations. Suspicious.
7. The Sea’s Strangest Square Mile: https://vimeo.com/59168847

A short documentary that shows some of the oceans most unique life forms.
8. Casanova: http://www.ferryhalim.com/orisinal/g3/casanova.htm

A game about a happy giraffe kissing other happy giraffes.
9. Muffin Films: http://www.muffinfilms.com/

A collection of muffin based animations.
10. Ripe Near.me: http://www.ripenear.me/

Here you can find locally grown products near you.
11. NASA Guide To Air Filtering House Plants: https://www.lovethegarden.com/community/fun-facts/nasa-guide-air-filtering-houseplants

Learn which plants clean the air, each plant takes out different harmful molecules.
12. The Last Samurai: http://www.addictinggames.com/action-games/the-last-samurai-game.jsp

A flash game where throw ninja stars and grenades to finish the level.
13. Your Game Is Too Big: http://yourgameideaistoobig.com/

This will help you estimate how much your game will cost depending on what features you want.
14. Moonstruck: http://www.genvid.com/moonstruck/downloads/fonts.html

This website lets you download game fonts for you to use.
15. Strip Generator: http://stripgenerator.com/strip/create/

Lets you create your own custom comic strips.
16. Drift: http://www.koert.com/work/drift/play.php

An interactive music video that turns your mouse into an eyeball which can change the animation.
17. Yes No If: http://yesnoif.com/

Each time you click it modifies the triangles.
18. Has The Large Hadron Collider Destroyed The World Yet?: http://hasthelargehadroncolliderdestroyedtheworldyet.com/

Already covered some time ago in: How Secure is Your Password? And 21 Other DONGs.
19. Zombie Infestation Simulator: https://mattbierbaum.github.io/zombies-usa/

A website that lets you simulate how long it would take for the zombies to destroy USA. It's actually pretty slow.
20. Aug(De)mented Reality 3: https://www.youtube.com/watch?v=nJwpKQMbREw

A video that combines drawings with real life.