Skip the login form: every visitor automatically auths as an admin. FOR 'LOCALHOST' TEST SITES only, obviously, like when designing a plugin or a theme and testing it across various browsers.

For a hassle free integration, drop the plugin file into wp-content/mu-plugins (create the directory if needed) and it will be automatically activated.

For live blogs, see Always Remember Me

Installation is, as usual :

1. Upload files to your /wp-content/plugins/ directory (preserve sub-directory structure if applicable)
2. Activate the plugin through the 'Plugins' menu in WordPress
3. Refer to the official plugin page for documentation, usage and tips

Everybody is the admin.