How Secure Is My Password? is a great little site that Kern Kelley showed off at the Google Apps Bootcamp in New Hampshire today. How Secure Is My Password? allows you to see how long it would take a person or a computer to guess your password. One of my passwords would take 2 million years to crack.
Make Me A Password is the sister site to How Secure Is My Password? As the name implies, Make Me A Password will generate a secure password for you.
Applications for Education
How Secure Is My Password? could be a good tool for showing students and colleagues how strong or weak their passwords are.
Watch Common Craft's video on secure passwords for a good video overview of what makes a password secure.