The Boehm-Demers-Weiser conservative garbage collector can be used as a garbage collecting replacement for C malloc or C++ new. It is also used by a number of programming language implementations that use C as intermediate code. Alternatively, it may be used as a leak detector for C or C++ programs. A slightly older version of the garbage collector is also included as part of the GNU compiler (gcc) distribution.
Unifdef is useful for removing #ifdef'ed lines from a file while otherwise leaving the file alone. You specify which symbols are defined or undefined with -D and -U flags, and unifdef removes the corresponding ifdefs, and the enclosed code if appropriate. It's especially useful for removing those "#ifdef BROKEN" and "#ifdef PRIVATE" clauses from code before you release it. Unifdef acts on #if, #ifdef, #ifndef, #elif, #else, and #endif lines, and it knows only enough about C and C++ to know when one of these is inactive because it is inside a comment or a single or double quote.
GLE (Graphics Layout Engine) is a graphics scripting language designed for creating publication quality figures (e.g., a chart, plot, graph, or diagram). GLE supports various chart types (including function plot, histogram, bar chart, scatter plot, contour plot, color map, and surface plot) through a simple but flexible set of graphing commands. More complex output can be created by relying on GLE's scripting language, which is full featured with subroutines, variables, and logic control. GLE relies on LaTeX for text output and supports mathematical formulae in graphs and figures.
AweMUD is a MUD server for use with fantasy-settings. Features include fully dynamic objects and characters, an advanced scripting system, and custom worlds. The engine will eventually have completely interactive rooms (items can be placed under benches, doors can be destroyed), complex magick, and interactive NPCs.
QuantLib is a cross-platform, quantitative finance C++ library for modeling, pricing, trading, and risk management in real-life. It is also wrapped as Python/Ruby/Scheme modules. Extensions for Excel, R, and Mathematica are available. Other such extensions are under consideration. QuantLib offers tools that are useful both for practical implementation and for advanced modeling. It features market conventions, yield curve models, solvers, PDEs, Monte Carlo (low-discrepancy included), exotic options, VAR, and so on.