Blitz++ is a C++ class library for scientific computing which provides performance on par with Fortran 77/90. It uses template techniques to achieve high performance. Blitz++ provides dense arrays and vectors, random number generators, and small vectors (useful for representing multicomponent or vector fields).
The Extension Pack for UT99 is an SDK full of new features/tools improving the Unreal Engine 1 in a wide range. Besides tons of new visual features it improves physics, gameplay and AI, contains a new render (currently OpenGL only) and bundled tools.