Hutch is a Ruby library for enabling asynchronous inter-service communication in a service-oriented architecture, using RabbitMQ.
CodeCube is a code-snippet editor that allows you to run the code and see the results in real time. It's built on Docker and Go, and is open source on GitHub.
Rig is a tool written in Go, that helps you to run and manage services on your development machine. It's a bit like pow.cx, but it works with any language.
MongoEngine is an Object-Document Mapper (think ORM, but for Document Databases) for working with MongoDB from Python. The documentation is available at mongoengine.org/docs and the source is available on GitHub.
Mumblr is a simple Tumblelog application, written in Django. It uses MongoDB as its database, and MongoEngine for communicating with MongoDB from Django. Fork it on GitHub.
A Django email backend that provides support for Amazon's Simple Email Service.
An extension panel for Rob Hudson's Django Debug Toolbar that adds MongoDB debugging information.
Chrome extension that allows you to save cookies for a website to a "profile", then easily switch between your saved cookie profiles. Find out more.
FireSheep, but for Google Chrome. It has two components—a server, written in CoffeeScript and Node.js, which sniffs sessions over a given network interface, and a Chrome extension that activates the sniffed sessions in the browser. Find the source on GitHub.