MacPython 2.3 installs a perfectly normal Unix commandline python interpreter in /usr/local/bin/python. As of Mac OS X 10.2, however, /usr/local/bin is not on the search path of your shell. Moreover, Apple's python 2.2, which lives in /usr/bin is on your search path, so this can lead to confusion.
If you use tcsh you should add the following line
to the file .login in your home directory and restart Terminal:
setenv PATH /usr/local/bin:$PATH
If you use bash or zsh
you should add the following line
to the file .profile in your home directory and restart Terminal:
export PATH=/usr/local/bin:$PATH
GUI scripts
Due to the way MacOS handles windowing applications you need to run all scripts that use the window manager (be it through Carbon, Cocoa, Tkinter, wxPython, PyOpenGL or anything else) with the pythonw interpreter, also installed in /usr/local/bin.
Running with python results in an inability to bring the script to the front, or interacting with it.