You can add the number of blogs, number of users and most active blogs (with post count) on your backend by using a somewhat hidden function un wpmu: get_sitestats()
Open the wp-admin/wpmu-admin.php file and just after these lines:
switch( $_GET[ 'action' ] ) {
default:
paste the code here: http://ringofblogs.com/global_stats.txt
This is if you are using wpmu 1.0. If you are using rc4 just open wp-admin/wpmu-admin.php and you will see the code and know what to do.
Hope it helps someone :)