The 2DECOMP&FFT library is a software framework in Fortran to build large-scale parallel applications. It is designed for applications using three-dimensional structured mesh and spatially implicit numerical algorithms. At the foundation, it implements a general-purpose 2D pencil decomposition for data distribution on distributed-memory platforms. On top, it provides a highly scalable and efficient interface to perform three-dimensional distributed FFTs.
6jack is a framework for testing, analyzing, and fuzzing network applications. 6jack runs a command, intercepts calls to common network-related system calls, and passes them through an external filter. A filter can be written in any language supporting the MessagePack serialization library. 6jack is especially useful for writing tests for clients and servers, debugging and reverse engineering protocols, sketching filtering proxies, and fuzzing.
AEditor is a programmer's editor for Windows, Unix, and Mac OS X that relies on the fox toolkit. It can do syntax coloring of Ruby and C++ files. It's easy to change the color theme. Most things are customizable. It is written in Ruby and is carefully unit-tested (it has 421 tests). It is written in only ~5500 lines of code, so it should be easy to grasp and extend.
AFNIX is a multi-threaded functional writing system with dynamic symbol bindings that support the object oriented paradigm. It has a rich set of features providing runtime compatibility with C++. The engine runs on both 32- and 64-bit platforms, and it is designed to be portable across platforms.