Vitor Carvalho

This plugin is DEAD until further development. 
Don’t use it as this can lead your WordPress instalation into problems.
With this plugin you can change wp-admin and wp-login.php to any of your choice. 
You can have <code>http://example.org/login</code> instead of <code>http://example.org/wp-login.php</code> or <code>http://example.org/admin/</code> instead of <code>http://example.org/wp-admin/</code>
You just need to enter into <code>options-permalink.php</code>page and set the variables. 
After the setup wp-login.php and wp-admin path are not anymore available and you should use the newest onews you set.
This works with Multisite Networks. You can set a default value in Options page of Multisite settings section.
Languages available: English, Português, Español, Italiano, Deutsch.

Custom Login and Admin URLs (CLAU)

AVOID TO USE THIS PLUGIN! Change wp-admin and wp-login URL to any of your choice. Security by obscurity!

Webtronic

A simple plugin that allows web developers and designers to brand the login page of WordPress for their customers.
You can upload a logo, background image, change colors and add custom CSS and JavaScriptto the wp-login.php form.

WP Custom Login Branding

A simple plugin that allows web developers and designers to brand the login page of WordPress for their customers.

Custom Login and Admin URLs (CLAU) vs WP Custom Login Branding