The 1Password browser plugin is great for generating strong randomly generated passwords. Did you know that you can add your own customization to the generated passwords or test your own for strength?
In Safari, just open the password generate and generate a new password. Now click in the text box and add any string to it you like.
If you want to test your own password, delete the generated one and type in yours. 1Password will show just how bad it is.
This also works in the 1Password Mac app.
On iOS and 1Password 4, you can manually override or edit a generated password, but the strength indicator does not update.