The Google SparseHash project contains several hash-map implementations in use at Google, with different performance characteristics, including an implementation that optimizes for space and one that optimizes for speed.
Orange is a component-based data mining software. It includes a range of data visualization, exploration, preprocessing and modeling techniques.
NetworkX is a Python language software package for the creation, manipulation, and study of the structure, dynamics, and function of complex networks.
NLopt is a free/open-source library for nonlinear optimization, providing a common interface for a number of different free optimization routines available online as well as original implementations of various other algorithms.
BLAS provides standard interfaces for linear algebra, including BLAS1 (vector-vector operations), BLAS2 (matrix-vector operations), and BLAS3 (matrix-matrix operations).