zxcvbn (https://dl.dropboxusercontent.com/u/209/zxcvbn/test/index.html https://dl.dropboxusercontent.com/u/209/zxcvbn/test/index.ht..., https://github.com/lowe/

zxcvbn (https://dl.dropboxusercontent.com/u/209/zxcvbn/test/index.html https://dl.dropboxusercontent.com/u/209/zxcvbn/test/index.ht..., https://github.com/lowe/zxcvbn https://github.com/lowe/zxcvbn) basically has this aim. It might be missing some patterns exploited in attacks, but it’s extensible enough that they shouldn’t be too hard to add.