The short version is that Numeric was the original package that provided efficient homogeneous numeric arrays for Python, but some developers felt it lacked certain essential features, so they began developing an independent implementation called numarray. Having two incompatible implementations of array was clearly a disaster in the making, so NumPy was designed to be an improvement on both.
Neither Numeric nor numarray is currently supported. NumPy has been the standard array package for a number of years now. If you use Numeric or numarray, you should upgrade; NumPy is explicitly designed to have all the capabilities of both (and already boasts new features found in neither of its predecessor packages). There are tools available to ease the upgrade process; only C code should require much modification.
