ExpressionEngine is having a large number of Standard Global Variables which can be used within the templates. You can find all these from http://ellislab.com/expressionengine/user-guide/templates/globals/single_variables.html.
The available member variables can be much useful:
- logged_in_member_id
- logged_in_group_id
- logged_in_group_description
- logged_in_username
- logged_in_screen_name
- logged_in_email
- logged_in_ip_address
- logged_in_location
- logged_in_total_entries
- logged_in_total_comments
- logged_in_private_messages
- logged_in_total_forum_topics
- logged_in_total_forum_replies
- logged_in_total_forum_posts