This stay-open applet watches your playing tracks and when an un-rated track starts playing displays a window with a demand it be rated.
While you could easily rate the current track from the iTunes icon in the Dock, this script interrupts you and compels you to do so.
OS X 10.6 or better only. Previous universal version available at the link below in the "Info" section.
This window will pop up when a new song begins playing.
Remove iTunes tracks disassociated from files
Append user-entered text to beginning or ending of selected tag of each selected track
Resample selected tracks' artwork to user-set size limit
Delete characters from the beginning or ending of selected tracks' name, artist, album, comments, composer, or show tags
Rename selected tracks' Song Names with their filenames (minus extension)
App displays files in iTunes Media folder which are not in iTunes library