Statistics-Descriptive is a Perl module to perform Statistical Analysis on numeric data. It can retrieve such things as the mean (or average), the median, the standard deviation, a histogram/frequency analysis, etc.
APreL++ (Arbitrary Precision Library for C++) provides classes for manipulating arbitrary precision numbers. It is based on C++ string manipulation.
A simple digital sound signal editor for KDE
A control protocol for various astronomical instruments (telescopes, CCDs, etc).