The TeXmacs community manages two containers of TeXmacs-related content.
texmacs/tm-forge : a repository of user contributed content for TeXmacs: examples, style files, templates, macros, etc… You can find it here:
Contribution in the form of pull requests in GitHub are welcome. You can also reply to this message in the forum with content you would like to suggest for inclusion.
texmacs/notes : a TeXmacs blog
which accepts proposal for articles, additions, etc…