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.

The P-Login allows you to create unique & stylish login page. And it’s very easy in use. You just need to upload your images or choose color for elements of login page on the plugin options page.

P-Login

The P-Login allows you to stylize login page.  You can upload images or choose the color of backgrounds and text for login page elements.

Login XChange vs P-Login