Vagrant is a tool for building and distributing environments
A simple, Git-powered wiki with a local frontend
Chrome extension for Rails development
Better error page for Rack apps
Snd is a sound editor
Fast, Nimble PDF Writer for Ruby
Marathon supports testing of Java/Swing and Java/Fx applications.
Music score editor
Draw railway tracks in 3D from a simple script language in SketchUp
PIM/shcedular
"DYI for Rails" is a library for use DYI on Rails.