Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
GitNews Web - Trending repositories from GitHub, HackerNews & Reddit
Octoview - The missing preview feature for GitHub
LibHunt - LibHunt tracks mentions of software libraries on relevant social networks. Based on that data, you can find the most popular projects and their alternatives.
Dyllo - A clean and simple way to view a Github user's information
Ruby Toolbox - Explore and compare open source Ruby libraries