Xapian is a search engine library, scalable to collections containing hundreds of millions of documents. It's written in C++ with bindings for Perl, Python, PHP, Java, Tcl, C#, Ruby, and Lua. It is a highly adaptable toolkit that allows developers to easily add advanced indexing and search facilities to their own applications. It supports the Probabilistic Information Retrieval model and also a rich set of boolean query operators. Omega is a Web search application built upon the Xapian library. It can index a Web server's document tree (including HTML, PDF, OpenOffice, MS Word/Excel/Powerpoint/Works, WordPerfect, RTF, PS, etc.), or data exported from arbitrary sources (e.g. SQL databases).
C/Invoke is a library which can call C functions at runtime with no prior knowledge of the function prototypes. This capability is used to allow any language to call native libraries without writing a separate module in C, similar to the P/Invoke functionality of the .NET framework.
Scrupp is a 2D engine that uses OpenGL for hardware-accelerated visualization. All of its functionality is exported to the Lua programming language. Using Scrupp means writing Lua scripts. It features support for movies and networking and enables run-time image creation using Cairo.
MySQL Workbench is a cross-platform, graphical database modeling tool for MySQL. It allows you to create database models from scratch as well as by importing existing databases from SQL or DBDesigner4 models. You can then generate SQL code to CREATE databases, ALTER them, and export in various image formats and PDF/PS. Its extension system allows writing plugins and scripts in Lua, Python, and C++.
The Crate Game Engine is a game engine that is designed to make creating games trivial. The rendering and scripting engines are removed from the game engine to make the specialization of games as easy as possible. Currently, scripting support is implemented to allow a Lua script to be put directly in the game file, which can be validated as XML. Multiplayer text based adventure-style games can be played with the existing console rendering engine.