Macports? Binary? RVM-esque tool? Other?
I will be using NumPy/SciPy for a computer vision project, so I want to do it once and do it right.
do it with the scipy superpack, by Chris Fonneback. It's very easy, automated and it works (using it right now!).
It also takes care of installing Fortran for you, which is mandatory for the python libraries to work.
PS: If you have Lion, Numpy is already part of it.
Depends on what else you want to do.
the simplest is probably the binary Enthought distribution especially in the paid for versions - the free version will give you matplotlib, numpy and scipy in 32 bit which might be sufficient for you.
If you need other C libraries then macports (and I suspect fink, homebrew) will work. Note that for Lion and 64 bit python you might have to install matplotlib with no tk support (tk is one of the possible gui libraries) e.g.