Password Meter measures a wide range of password metrics and gives them weighted values. It’s quite thorough.
Apart from strong passwords the following tips are useful:
- Ensure nobody watches you type in your password
- Keep your computer safe from key-logging programs. Use a good anti-spyware tool for this
- Change your password often (every 1-2 months)
- Don’t log into important sites on a public computer, such as at an internet cafe. Important sites include online banking sites, eBay, or any sites where money transactions can occur
Password Meter’s site is here.