GitNews Web - Trending repositories from GitHub, HackerNews & Reddit
Gitstalk - Discover what your favorite GitHub users are up to
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.
Refined GitHub - Browser extension that makes GitHub cleaner & more powerful
Ruby Toolbox - Explore and compare open source Ruby libraries
Dyllo - A clean and simple way to view a Github user's information