grunt-rsync and its sister package rsyncwrapper are two npm modules that I actively maintain on GitHub. I created these packages a few years ago while starting out with Node.js and npm and I had a need to make use of the rsync tool as part of a Grunt-based deployment pipeline.
With the benefit of increased experience I now question the wisdom of wrapping a cli tool like rsync in Node.js. But nevertheless the plugin scratches an itch for many, it's downloaded over 3K times per month, it's used by Opera to deploy their dev.opera.com site (!) and I've received many contributions and pull requests. It was a great opportunity for some active experience in the GitHub open source community.