GitHub has an Atom feed for tags so you can subscribe to them with your RSS reader. The format is:
This is useful for projects that don't use Releases. For example Elixir packages tend to use tags and then release on Hex (which as far as I can tell doesn't have any way to be notified of new releases).
If the project you're following uses Releases then you can use GitHub's built in 'Watch' feature:
If you like Atom / RSS feeds there are more available on GitHub:
/* Repo releases */ https://github.com/:owner/:repo/releases.atom /* Repo commits */ https://github.com/:owner/:repo/commits.atom /* User activity */ https://github.com/:user.atom