To try any of the examples, copy them over to:

    /usr/lib/nautilus/extensions-1.0/python/
or:
    ~/.nautilus/python-extensions/

Then restart nautilus.

Hint: if you're testing an extension that you're developing, it may
be useful to start a 'private' instance of nautilus, like this:
  $ mkdir /tmp/testing
  $ export TMPDIR=/tmp/testing
  $ nautilus --no-desktop