clipcaptcha by Foundstone is an extensible and signature based CAPTCHA Provider impersonation tool based off Moxie Marlinspike's sslstrip codebase. Depending on its mode of operation it may approve, reject or forward the CAPTCHA verification requests. It maintains an easy to edit XML configuration file that it queries to identify CAPTCHA provider request formats and render corresponding responses.
Python 2.5 or newer
Twisted Python Module