I have been involved as a developer in Open Source projects for 10 years. Some of the projects to which I contributed code:

• JRuby – a pure-Java implementation of the Ruby programming language. (I started this project 2001 and was lead developer for 3 years)
• GNOME Control Center (I added a D-Bus interface to support multimedia keys)
• GTK+ – a highly usable, feature rich toolkit for creating graphical user interfaces which boasts cross platform compatibility and an easy to use API.
• Nautilus – a graphical shell for the GNOME desktop enviornment that makes it easy to manage your files and the rest of your system.
• Totem – the official movie player of the GNOME desktop environment.
• GPE - a collection of integrated software components optimized for handheld and other input constrained and resource limited devices. (I added support for specific Hildon-widgets to gpe-contacts and libgpepimc)
• FreeCiv – a Free and Open Source empire-building strategy game inspired by the history of human civilization.
• GnuCash – a personal and small-business financial-accounting software. (I contributed an advanced UI plugin system)