PassReview is a jQuery plugin that allows you to easily integrate powerful password validation into your forms.
Key features:
Smart, multi-parameter password strength evaluation. Computation of the cryptographic password strength (entropy) according to the NIST Special Publication 800-63. Shows an estimate of the password hash cracking time on modern hardware.
Helpful password strength advices to guide the user. Control the minimum number of letters, numbers, unique characters and alternating case letters in a password. Easy integration and cross-browser compatibility (including IE6 ).