To continue my emphasis on the importance of password strengths, you can now quickly and easily check the quality of your passwords using Password Meter. This is a good cross-platform compatible solution, and allows users to understand how the strengths of passwords are calculated. Although no official weighting exists, the values they use seem very reasonable to me.
Although the script does not appear to send the tested passwords anywhere, this can easily change without notice. So always err on the side of caution, and use this to help you understand how to create a good password. Then create one equally strong in your head.
Note: for those of you who use Mac OS X, the built-in Password Assistant is quite good.
Those of you who require ultra-strong passwords, for use with encryption schemes for example, check out Steve Gibson’s Ultra High Security Password Generator.