SmallDevTools - Handy developer tools with a delightful interface
GitNews Web - Trending repositories from GitHub, HackerNews & Reddit
Google Open Source - All of Googles open source projects under a single umbrella
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.
whatdevsneed - This is whatdevsneed.
Ruby Toolbox - Explore and compare open source Ruby libraries