MathGL is a library for making high-quality scientific graphics under Linux and Windows, fast data plotting and handling of large data arrays, working in window and console modes, and easily embedding into other programs. It has more than 40 general types of graphics for 1d, 2d, and 3d data arrays. It can export graphics to raster and vector (EPS or SVG) formats. It has an OpenGL interface and can be used from console programs. It has functions for data handling and MGL language scripting for simplification of data plotting. It has several types of transparency and smoothed lightning, vector fonts and TeX-like formula drawing, an arbitrary curvilinear coordinate system, and many other useful things.
Seamstress is a portable library that implements Avidan and Shamir's seam carving technique for content-aware image resizing. Seam carving works by removing the "boring bits" from an image, so it can change the aspect ratio of many images without changing the shape of the objects inside.
xTests is a small, simple, lightweight, portable unit/component testing library for exercising C and C++ libraries. It relies on no platform-specific or compiler-specific constructs and doesn't require pre-processing of your source code by scripting languages or use macros to create secret classes that use Schwarz counters to register test cases. It relies on you to simply code what you want, and nothing that you don't want.
Python bsddb3 is a Python module that provides a nearly complete wrapping of the Oracle/Sleepycat C API for the database environment, database, cursor, sequence, and transaction objects, and each of these is exposed as a Python type in the bsddb3.db module. The database objects can use various access methods: btree, hash, recno, and queue. It has complete support for Berkeley DB distributed transactions, and complete support for the Berkeley DB Replication Manager and base replication API. The goal is to mirror most of the real Berkeley DB API.
vov (Vov's Obsessive Von-neumann) is a tool that emulates the behavior of a von Neumann machine. It is basically an interpreter that reads files in the form of memory assignments and executes the encoded instructions. The vov's instructions allow you to perform simple arithmetic data manipulation. It is a very useful tool to see if your programs work and how. You can run a vov program from a file as you would any other shell, Perl, Python, or Ruby program.