Overview of which sites use a PHP version
The usage counter in server_php_list.php from server_php_list.php !991 (merged) helps to see how many sistes use the version but not which sites. And I did not find an easy way to look this up.
Adding an extra column to the sites list was my first though as that would allow filtering on php version. But I see two objections, first not all sites have the setting(either using mod php or no php at all), and second it would compete for space in an already filled table.
I suggest adding a simple list on the Additional PHP Versions edit form. Additional styling is very welcome ;)