Redux-Tiles - Library built on top of Redux to make it less verbose and otherwise better. I don't know enough yet to know if this is significant. I have a feeling I'd better learn, though.
asdf - An extendable version manager with plugins to handle all sorts of languages. Sort of like rvm or rbenv but for everything.
Tracebin - Easy & free application monitoring for Rails/Rack apps (as long as you don't need more than 24 hours of data).
terraform and GitHub labels - A tiny example showing how you can use this tool for a simple maintenance task.