Vast HTML

This is a full featured plugin to help you edit your login just the way you want it. Lets you use or block the original wordpress 
css (the first plugin to do this). Comes with one pre made style you can use or deactivate. 
Very easy to create your own style using the style tags givin in the plugin. 
Please visit http://vasthtml.com/js/login-xchange-plugin/ for usage instructions.

Login XChange

This plugin will let you change the css of your login and register pages.

Muhammad Alnajlat

Light, fast and easy-to-use plugin for branding WordPress login page by setting your brand logo and theme color and extra simple styles.
What you can do with Brand My Login:
<ul>
<li>The simplest things you need to brand your login page.</li>
</ul>

Brand My Login

Brand and style your WordPress login page quickly and lightly.

Login XChange vs Brand My Login