any examples of great well-written web apps?

[Python Baby]

learning Python, planning on making an interactive website.

To me, "interactive website" = "web app" = websites such as
NetFlix, Amazon, Orbitz, Hotmail, MyYahoo, etc.  Something
stateful that does a lot behind the scenes, but uses the 
web browser as an interface.

Has anyone seen any great examples of very well-written web
apps like this, in Python, that I could study the source?
(Preferably not as huge as the examples I named above.
I was just picking popular examples.)

The reason I'm asking the list instead of just browsing
Freshmeat or Sourceforge is that since I'm new to Python,
I won't know the difference (at first) between well-written
Python and clunky Python.  Looking for a website-service
that is a good example of a good use of Python.

(Getting used to "thinking in Python").

Thanks!