IKVM.NET is a JVM for the Microsoft .NET Framework and Mono. It can both dynamically run Java classes and can be used to convert Java jars into .NET assemblies. It also includes a port of the OpenJDK class libraries to .NET.
The freeWrap program turns TCL/TK scripts into single-file binary executable programs. freeWrap can wrap TCL/TK applications that consist of multiple script and binary files. freeWrap combines all the files together into a single executable file.
A general extension language system based heavily off of the Quake 3 Virtual Machine and Q3 SDK Toolkit.
Glue code for hooking together CodeViz and GraphViz to have very customizable call graphs. Directions are on http://viz-duct-tape.sourceforge.net
ePolyglot is a set of libraries, classes, and tools which enable Eiffel to interoperate with Python and, to an extent, Haskell. Features for using Python objects from Eiffel, Eiffel objects from Python, and Haskell functions from Eiffel are included.