It’s quite hard to find good free tools that support work within STEM subjects so it was a nice suprise to come across https://www.circuitlab.com/.

Not only is it a flexible and very easy to use analogue and digital circuit simulator but the tool also allows users to share their work online inviting comments and suggestions from others. One of the things I really liked was that everything was online – no software to download, no complicated set-up just an extremely intuitive interface allowing users to try out their ideas with the minimum of fuss – great stuff.