Useful web tools I have found for maths. In descending order of how well known they are (approximately)

General Tools

  • randoma11y: Generate random color schemes with sufficient color contrast
  • MyOSMatic: Generate your own map from OSM
  • Microsoft Paint Online: Open-Source, Web Components-based remake of MS Paint using modern web capabilities

Thanks to Isaac Li for telling me about Field Play and randoma11y.