I do not yet have much stuff here, but be sure to check out these cool places:
- Tcl/Tk and its mirror here in GitHub
- A lot of packages for Tcl can be found on the page of the "Github Tcl organization"
- fossil SCM and its mirror here on GitHub
- CommonMark is the place to start when you want to work with any markdown project
- SubEthaEdit is a nice and light-weight macOS editor also supporting markdown including a preview feature that is highly customizable. It uses the showdown parser written in Javascript
- see here