I see that there is something similar in the latest SVN trunk (btw, this is how I found out 'password' is not a third-party plugin, is in core :p). But it only accepts minimum size for password and the presence/absence of other chars than alphanumeric.
This should be expanded as I said above:
- test for alpha parts of username bigger than 3 not to be included in password (if username is "user.name.xx.2009", test for "user" and "name")
- minimum number of digits
- minimum number of another non-alphanumeric characters
Also, it would be nice to test for presence of certain white spaces ("\n", "\r", "\t") and warn/disallow to change in that case. Very useful if a user notes down in a file a password, and copy-pastes it with line-endings/spaces. Then, when writing it down by hand in the password box, he/she can't login and doesn't know why (it happened...)