In the programming community there are a few useful ways to find out about new software. Blogs and news sites like Hacker News, Reddit and Slashdot are good for learning new tools and techniques, but it is fairly random that you would learn something relevant.
GitHub Explore is also where you’ll find the more complete GitHub Search, for when you want to find something very specific.
When you find something you like, be sure to star it. That makes it a lot easier to find it later, and also gives the repository a little more visibility. More stars means more eyeballs, which means potentially a post on Hacker News or Reddit, which means more stars, and so on. It’s a vicious cycle!