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.

parswp

<h4>A must have plugin for wordpress blogs</h4>
By using Hide Login+ you can simply change most important URLs that are being accessed every day, keeping them safe and secret.
For those upgrading from previous version: please check installation steps
New features:
<ul>
<li>No need to modify <code>wp-config.php</code> any more (see installation steps)</li>
<li><code>.htaccess</code> backup file is created before changes take effect (named <code>.htaccess.backup</code>)</li>
<li>Recoded to be latest WordPress version compatible</li>
</ul>
Benefits:
<ul>
<li>Have secured and hidden login page</li>
<li>Customized URLs for the most important parts of your WordPress installation</li>
<li>Control access over <code>wp-login.php</code> and <code>wp-admin</code> pages</li>
<li>Easy back-to-defaults ability without frustration</li>
</ul>
Features:
<ul>
<li>Define custom URL slug for login, logout, registration, lost password & admin pages</li>
<li>Able to prevent access to <code>wp-login.php</code> and <code>wp-admin</code> directly</li>
<li>See your <code>.htaccess</code> content after changes have been successfully updated.</li>
<li>
Revert to default configurations on plugin deactivation (or easily via a second method)
This won’t secure your website perfectly, but if someone does manage to crack your password, it can make it difficult for them to find where to actually login. This also prevents any bots that are used for malicious intents from accessing your <code>wp-login.php</code> file and attempting to break in.
</li>
</ul>

Hide Login+

Have a secure login and admin page. Allows you to create custom URLs for user's Log in, Log out, Sign up and Admin page.

Login XChange vs Hide Login+