If you have something that is parsing our json-API here, you can always see which sites we are actively supporting to follow. Otherwise, this page is a first intro of what's offered.
You can always contact firstname.lastname@example.org if you have more suggestions of sites that should be monitored.
This may sound a bit contra productive with the fact that there may already exist RSS feeds for things we monitor. However, in that case, this feed fetcher is instead built for merging several RSS feeds into one big compilation. There are not very many resources available here, at least not publicly.