Google Open Source - All of Googles open source projects under a single umbrella
Flox - Manage and share development environments with all the frameworks and libraries you need, then publish artifacts anywhere. Harness the power of Nix.
Opensource Builders - Find open-source alternatives to commercial apps
whatdevsneed - This is whatdevsneed.
LaunchKit - Open Source - A popular suite of developer tools, now 100% open source.
SmallDevTools - Handy developer tools with a delightful interface