The ArcGIS Python 2.7 distribution for 10.1 includes (in addition to the python standard library) the user-contributed modules numpy and matplotlib. It would be really great to include some more modules. If you agree, vote this item up and add your favorites (and use cases) in the comments.
My list of of modules I'd like to see includes:
If you are interested in what these all are, I pulled these off the list of what's included in the current Enthought Python Distribution.