I noticed on Slashdot an entry on the Open Library and it mentioned Aaron Schwartz. Assuming it was the Aaron Swartz of web.py (which reddit was somewhat famously rewritten from Lisp into Python using), I decided to poke around and see if the technology behind the Open Library was discussed.
Turns out it is. If you look at the favicon for the source code browser you will notice it is Mercurial. And if you look at the file names (let alone what they contain) and the configuration files you will notice the site is running Python through Lighttpd over FastCGI.
I just hope they open up a bug tracker so I can report my first bug: an unneeded 'sys' import in their point of entry. =)