1. Useless Facts: https://uselessfacts.net

Did you know that a group of cats is called a clowder? Although that might seem like an useless fact...s.net.
2. Sound in Color: https://www.hpsoundincolor.com

Record a song and watch it make a painting based on what it hears.
3. Giorgio Cam: https://aiexperiments.withgoogle.com/giorgio-cam/view/

Take a photo of anything you want and the site will make a song about it.
4. Gaia 3D Star Map: http://charliehoey.com/threejs-demos/gaia_dr1.html

This site contains the position of 2 million stars.
5. Make Mars Home: http://www.makemarshome.com/landing

This site gets you prepared to live on the red planet by going through your qualifications and skills.
6. Brain Model: http://www.finr.net/files/brain/index.htm

An interactive diagram of the human brain.
7. Airview: https://airview.blueair.com/view/Tb9fmd_OcEi7WhAArAcXVQ

Shows you what pollutants are in the air we breath, you can go to any city to see what's there.
8. Where is Cat?: http://www.kongregate.com/games/bontegames/where-is-cat

You need to find whatever the cat needs, kind of like "Where's Waldo".
9. Ugly Sweater: http://uglysweaters.work

You can design your own ugly christmas sweater.
10. Verdant Labs: http://verdantlabs.com/professions/index.html

This chart shows you which names are most likely to have certain professions.