Asymptote is a powerful descriptive 2D and 3D vector graphics language for technical drawing, inspired by MetaPost but with an improved C++-like syntax. It provides for figures the same high-quality level of typesetting that LaTeX does for scientific text. Asymptote is a programming language as opposed to just a graphics program. It can exploit the best features of script (command-driven) and graphical user interface (GUI) methods. High-level graphics commands are implemented in the language itself, allowing them to be easily tailored to specific applications.
GNU TeXmacs is a free wysiwyw (what you see is what you want) editing platform with special features for scientists. The software aims to provide a unified and user friendly framework for editing structured documents with different types of content: text, mathematics, graphics, interactive content. TeXmacs can also be used as an interface to many external systems for computer algebra, numerical analysis, and statistics. New presentation styles can be written by the user and new features can be added to the editor using Scheme.
Armadillo is a C++ linear algebra library (matrix maths) aiming towards a good balance between speed and ease of use. Integer, floating point, and complex numbers are supported, as well as a subset of trigonometric and statistics functions. Various matrix decompositions are provided through optional integration with LAPACK and ATLAS libraries. A delayed evaluation approach, based on template meta-programming, is used (during compile time) to combine several operations into one and reduce or eliminate the need for temporaries.
Calc is arbitrary precision arithmetic system that uses a C-like language. It's useful as a calculator, an algorithm prototype, and as a mathematical research tool. More importantly, calc provides a machine-independent means of computation. Calc comes with a rich set of builtin mathematical and programmatic functions.
Botan is a crypto library written in C++. It provides a variety of cryptographic algorithms, including common ones such as AES, MD5, SHA, HMAC, RSA, Diffie-Hellman, DSA, and ECDSA, as well as many others that are more obscure or specialized. It also offers SSL/TLS (client and server), X.509v3 certificates and CRLs, and PKCS #10 certificate requests. A message processing system that uses a filter/pipeline metaphor allows for many common cryptographic tasks to be completed with just a few lines of code. Assembly and SIMD optimizations for common CPUs offers speedups for critical algorithms like AES and SHA-1.
DOLFIN is the C++ interface of the FEniCS project for the Automation of Computational Mathematical Modeling (ACMM), providing a consistent PSE (Problem Solving Environment) for solving ordinary and partial differential equations. Key features include a simple, consistent and intuitive object-oriented API; automatic and efficient evaluation of variational forms through FFC; automatic and efficient assembly of linear systems; and support for general families of finite elements.
Grlib is an implementation of generative grammars and turtle graphics. The grammars (Lindenmayer systems) are used to produce descriptions of three dimensional objects, and the turtle is used to display them (i.e., generate images in several forms, such as bitmap, PostScript, or OpenGL).
Ch is an embeddable C/C++ interpreter for cross-platform scripting, shell programming, 2D/3D plotting, numerical computing, and embedded scripting. It is the simplest solution to numerical computing and visualization in the domain of C/C++. It supports the ISO 1990 C Standard (C90), major features in C99 (complex numbers, variable length arrays or VLAs, type generic functions, long long data type, etc), classes in C++, and extensions to the C language like nested functions, string types, etc. It can be embedded in other applications and hardware and used as a scripting language. C/C++ code is interpreted directly with no compilation to intermediate code. It supports Linux, Windows, MacOS X, Solaris, HP-UX, and FreeBSD.