There is a new service called Sibbell that sends you emails when there are new releases for GitHub repositories that you either star or watch. It’s a free service.
We try for all of our R packages to tag each new version that goes to CRAN, and associate notes about what has changed with that version in the releases page for the package. For example, here’s the most recent release for rgbif
https://github.com/ropensci/rgbif/releases/tag/v0.8.6
If you are on Twitter, we announce all or most of these releases, so that’s one way. But if you aren’t, or prefer email, Sibbell is a great way to get notified when there’s new versions of rOpenSci packages.