WideStudio is an Integrated Development Environment (IDE) for building window applications in C++, Ruby, Python an Perl for Windows, MacOSX, Linux, FreeBSD, SOLARIS and other unix and BTRON and T-Engine. This is open and free (under MIT/X Consortiun Lice
Joint - An abstract interface to Java. Joint is an interface to JNI that provides access to objects in an object oriented fashion, allowing applications to forget about the details of JNI. First up - a powerful interface from Ruby to Java!
Ruby Inline's 13+ releases has been fully migrated to http://rubyforge.org/projects/rubyinline/ Please go there for more information. It just seems to work better over there. :/ (just click home page above)
Implementation of Fortran codes and other math routines in pure Ruby gems. The objective of this project is to combine the computational assets sitting in Fortran codes with the user-friendliness of a modern programming language.
Curupira is a powerful, full-featured, cross-platform, pretty-well-tested, well-documented and easy-to-use open source server application (shard emulator) for ultima online.
Rails web application for automating donations transactions.