Provided by the University of Colorado, a great collection of online simulations classified into Physics, Maths and Chemistry mainly (a bit of space and biology which could have been in physics or chemistry).
These are extremely visual, interactive and can be downloaded in several forms, to experiment alone, or be part of a classroom exercise or demo, so as a detailed explanation. Associated teacher’s ressources need a registration.
Train or learn on buoyancy, PH calculation, gravity, and much more.
From elementary school (we love the “Natural Selection” tool, where you watch bunnies multiplying and cross physical attributes … until you restrict food or introduce predators) to university (vibrations and much more).
Very very nice.