Radu Boncea Weblog

The script will:

connect via imap to gmail
select the imap directory TwitterFollow (you should filter twitter follow notifications and label them with TwitterFollow)
fetch the headers of all unread mails
retrieve the twitter user screen_name that is following you from the headers
attempt to create a friendship aka autofollow. If an error occurs is probably due to the fact [...]

Requirements:

a valid gmail account
label your twitter follow notifications (E.g. I use TwitterFollow)
mechanize : a stateful programmatic web browsing
libgmail : a GA reverse engineered library
python-twitter : a wrapper around the Twitter API

IMPORTANT: because Gmail does not provide an API and does not intend to do that because of the ads, hacking libgmail to fetch the threads [...]