A playground for creating and redeeming musig outputs
https://supertestnet.github.io/musig-playground/
This app lets you create musig transactions with your friends from the comfort of your browser. You can construct a custom musig spend on testnet and set parameters like how many people should participate. It also serves as a proof that you really can do musig in the browser.
BTW this is all based on Guggero's excellent javascript schnorr implementation: https://github.com/guggero/bip-schnorr