I recently got a second monitor and needed something to put on it when I wasn't using it, and I was shocked to find that data visualization websites and "web toys" are much rarer than they used to be.
So here's the list of websites I did find, focusing mostly on things that do not require constant input to continue to be interesting, and are web-based, so keep in mind they can go down at any time. (many gotten from a post by Simon Madine, 2012, many contributed by Mr.doob although I have included a selection below.)
Screensavers:
https://bouncingdvdlogo.com/ - Bouncing DVD Logo
https://1j01.github.io/pipes/ - Pipes by Isaiah Odhner
https://www.bryanbraun.com/after-dark-css/ - A Variety of Retro Mac Screensavers including flying toasters and aquarium! Thanks Bryan
https://peterned.home.xs4all.nl/demooo/ - 3D Globe by Peter Nederlof
http://theorigin.net/ablazejs/ -- Ablaze by Patrick Gunderson
http://www.chiptune.com/starfield/starfield.html - Starfield by Chiptune
https://mrdoob.com/lab/javascript/webgl/clouds/ - Clouds by Mr.doob
Toys: (Some also suitable for screensaver)
http://viz.runningwithdata.com/boids/ - Birds by Jason Sundram
http://www.thesinglelanesuperhighway.com/ - Single Lane Superhighway by Aaron Koblin and Mr.doob
https://lab.hakim.se/origami/ - Origami by Hakim El Hattab
https://mrdoob.com/lab/javascript/effects/solitaire/ - Solitaire by Mr.doob
https://mrdoob.com/#/117/fire - Fire by Mr.doob
https://mrdoob.com/lab/javascript/effects/branching/01/ - Branching by Mr.doob
News and Data Visualizations:
https://www.newsola.com/ - Newsola by Nick Nicholaou
https://www.flightradar24.com/ - FlightRadar24, realtime flight tracking
https://www.marinetraffic.com/ - Marine Traffic, realtime vessel tracking
https://cybermap.kaspersky.com/ - Cyberthreat Realtime Map
This Reddit Curated List of Realtime Visualizations including:
https://www.ventusky.com/ - Ventusky, showing wind and temperature
kaledo-art
romaincrisis
dededos
origamiaround
turnnoffyourmind
kianamaiart
