Single Sign On allows a user to only sign in once and be signed in automatically across different systems.
Currently supported systems include:
Wordpress
WHMCS
The plugin works over multiple instances of the same system, for example multiple Wordpress installations as well as between systems, for example between WHMCS and Wordpress.
Installation:
Upload the single-sign-on folder to the /wp-content/plugins/ directory
Activate the plugin through the 'Plugins' menu in WordPress.