The Activity Search returns a filtered list of Activities with columns like Name ( of the creator of the activity), the activity status, the activity type, and who the activity is assigned to; but it lacks a column for the 'Activity Targets' - the constituents with whom the activity is happening.
The search turns that around and lists all the targets for which the activity is about. In other words, if you filter for Bulk email activities, this search will return all of the targets of your bulk emails. Using this custom search ( I call it Activity Targets ), you can then use the 'actions' drop down to operate on those target contacts- tag, delete, send bulk email, etc. . (As opposed to acting on the creator of the activities, which is what the Activity Search does). Read more here: http://forum.civicrm.org/index.php/topic,20506.msg87564.html#msg87564
Place this file at civicrm/CRM/Contact/Form/Search/Custom/ActivityTargets.php
... and put this file at /civicrm/templates/CRM/Contact/Form/Search/Custom/ActivityTargets.tpl: