How Secure Is Your Password

http://howsecureismypassword.net/ is a nice little tool that says how long does a desktop PC would take to crack your password. It is based on a simple calculation that

time taken to crack = (number of possible characters ^ password length) / calculations per second

Of course, they take into consideration that most common words can be easily cracked.

Other interesting thing about this tool is that, web developers can download the jQuery plugin that runs this. It is called Chrono Strength and can be downloaded from here. You can use it in your project to validate the strength of the password provided via a form or at the time of sign up, etc.