Yet another emulator for the 6502 microprocessor. The site also has an interesting toy unix written in JavaScript.
One can play spacewar in the browser on http://www.masswerk.at/spacewar/ (found Wed Aug 26 16:25:57 2015) and with punch cards on
https://www.masswerk.at/keypunch/, https://www.masswerk.at/cardreader and https://www.masswerk.at/card-readpunch/ (found 2025-03-13 via https://www.tuhs.org/pipermail/coff/2025-March/002037.html and https://boingboing.net/2025/03/10/make-your-own-virtual-punchcard.html)