One cool feature we could add to Zend form is a password stength verificator ; it could use a little dojo / ajax to work (so it might concern only Zend_Dojo_Forms, but it's a nice feature on login forms.

This is a fairly commun feature on subscription forms : one progress bar that tells the strength of the password : weak/medium/strong. This feature could work with points : 1 point per character used ; with minimal password length 3 points per upper character 5 points per special character ;

Weak : under 4 points ; medium 5 points ; strong ; 12 points, etc.