Reader2twitter_appengine is a project mainly written in Python, it's free.
This is a google reader to twitter for appengine
This isn't an auto solution, you do need to get pubhubsubhub stuff to work manually using curl, I will try and post some docs. But once you get it flowing, it goes.
Right now it uses my url shortener tskr.us, but I would be open to accepting patches to support more.
It also right now uses just the title, or if you have left a comment it uses as much of the comment as it can fit.
Your content will be truncated to make sure there is enough room for the link.