I just see a lot of requests for macros, but not a central place for vetted/voted macros. Would accelerate people and security. There are collections of evil macros for security purposes, but not any central I can find for good ones. Maybe macro use is a small enough population to not inspire the work for a collection?
Excel VBA macro use is gigantic. Billions of files contain VBA. If you google for "vba macro library" you should find many hits. I cannot vouch for any because I've never tried one I'm afraid, since I can easily write my own :)