Set the Plays ("Play Count" before iTunes v9.2) of the selected tracks to a user-entered number (they will all be set to the same number). If this number is 0 then the Last Played date of each track will be erased. (iTunes has the ability to "Reset Plays" to 0 from a track's contextual menu.)
Also see New Last Played Date and Add or Subtract Play Count.
Search allmusic website (AMG) with data from selected or playing track
Delete empty playlists
List tracks not assigned to playlists
Copy chosen tag info from one set of tracks to a different set of tracks
Copy files of selected tracks to playlist-named folder
Copy selected CD's CD Text to the clipboard