Please fork and post your own! Others from this week:
Faraday is a rack-inspired API client library. It supports middleware and multiple backends. Like rack, it's the kind of thing that makes you wonder why no highly-skilled hacker built it sooner.
Middleware for Faraday, including Mashify, which wraps the response with Hashie.
sferik has done a couple of marvelous things to my favorite twitter API client library. He migrated its packaging system from jeweler to bundler and switched its HTTP client library from HTTParty to faraday.
Andre Arko gave a phenomenal presentation about Bundler at SunnyConf, starting with theory and proceeding to examples. During it, I learned about some really cool things that Bundler can do that I didn't know about. For instance, it can install from a git repo or a local directory.
Serve is a simple web server for development. To serve from the current directory, you go to the directory and type serve. Unlike one-line code snippets I run with ruby -e or python -c, I can recommend this to designers. It also processes certain file types, like haml, sass, and markdown.
I'm writing a library with both Ruby and JavaScript versions. To develop the JavaScript version, I'm using CoffeeScript for development and Jasmine for testing. For now I'm only using a web page to test, which I got by copying files from the examples and lib directories. I bring up this web page by going to the js/ directory on my project and running serve.