Numeric and Scientific
["Numeric"] - http://www.numpy.org/ -- Numerical Python adds a fast, compact, multidimensional array language facility to Python.
NumArray - http://stsdas.stsci.edu/numarray/index.html -- Numarray is a reimplementation of Numeric which adds the ability to efficiently manipulate large numeric arrays in ways similar to Matlab and IDL.
SciPy - http://www.scipy.org -- SciPy is an open source library of scientific tools for Python. SciPy supplements the popular Numeric module, gathering a variety of high level science and engineering modules together as a single package. SciPy includes modules for graphics and plotting, optimization, integration, special functions, signal and image processing, genetic algorithms, ODE solvers, and others.
ScientificPython - http://starship.python.net/~hinsen/ScientificPython/ -- ScientificPython is a collection of Python modules that are useful for scientific computing. In this collection you will find modules that cover basic geometry (vectors, tensors, transformations, vector and tensor fields), quaternions, automatic derivatives, (linear) interpolation, polynomials, elementary statistics, nonlinear least-squares fits, unit calculations, Fortran-compatible text formatting, 3D visualization via VRML, and two Tk widgets for simple line plots and 3D wireframe models. There are also interfaces to the netCDF library (portable structured binary files), to MPI (Message Passing Interface, message-based parallel programming), and to BSPlib (Bulk Synchronous Parallel programming).
Multi precision math
MultiprecisionSoftwareDirectory (http://www.nersc.gov/~dhbailey/mpdist/mpdist.html) - Python wrapping unknown
["MAPM"] (http://www.tc.umn.edu/~ringx004/mapm-main.html) - Python wrapping in progress
GmPy (http://gmpy.sourceforge.net/) - GNU Multiple Precision library wrapping
Links
["Scientific Computation Topic Guide"] (http://www.python.org/topics/scicomp) - no longer maintained, but might still be helpful.