A: 

the Python STDLIB

Corey Goldberg
I wish this was true.
Mike Graham
+1  A: 

You can't read too much source. I think a good idea would be to take some Pythonistas (Raymond Hettinger and Ian Bicking come to mind) and fish out their code from their projects or from other sources like ActiveState and go through them.

Noufal Ibrahim
A: 

I think that the Python interface for Redis written by Andy McCurdy is a superb example of how Python code should be written, packaged, and organized. Have a look at the source code for yourself!

jathanism
+2  A: 

Check out Flask's code, the comments on the release announcement noted that the code was very well written:

http://lucumr.pocoo.org/2010/4/16/flask-0-1-released

Armin, the author of Flask, also wrote Werkzeug, which I use a lot, and find very well written. Here is the source:

http://github.com/mitsuhiko/flask/blob/master/flask.py

Randy Syring
A: 

The Twisted code is pretty well-written, although it is a somewhat complex codebase.

mipadi
A: 

I know http://code.google.com/p/jaikuengine/ was ported to Google App engine by googlers, so there must be some good practices in there.

OscarRyz
+1  A: 

I vote for Django, maybe too much specific on web developing field.

pygabriel
Django is a great big app that has a lot of code - at this point much of it is legacy code and in need of cleanup. Nonetheless, a good example of a large application to poke around in.
Paul McMillan
A: 

Consider the stdlib, some modules more so than others. One project that I have found exemplifies good python coding practices is rietveld. Of course, good in one person's eyes is awful in another's.