What's an 'Active Users' Block I hear you say 
I'll show you 
It records the number of users that visited in the last 72 hours, and scrolls through them.
Can be found on the Home Page.
Edited Files:
templates/~ALL_THEMES~/~ALL_THEMES~.cfg
Created Files:
blocks/blocks_imp_users_visited.php
blocks/blocks_imp_users_visited.cfg
blocks/language/lang_english/lang_users_visited_block.php
templates/~ALL_THEMES~/blocks/users_visited_block.tpl
templates/~ALL_THEMES~/images/icon_scroll_pm.gif