This script will add or subtract a half-star from the ratings of the selected tracks. Ratings with half-stars appear with "1/2" appended to their ratings (see the screenshot). I highly recommend attaching a keyboard shortcut to this script for faster access.
iTunes 6.0.2 or later (I only discovered this in 6.0.2; it may work in earlier versions).
The scripts have also been posted on the Missing Menu Commands page as separate add and subtract actions.
Also see Assign Half-Star Rating.
Perhaps of Interest...
downloaded 13m 56s ago
Play through each track in a playlist at your set interval
downloaded 18m 51s ago
Display, create text file listing info of dead tracks
downloaded 33m 28s ago
Export album artwork as folder.jpg to Album folder
downloaded 1h 8m 30s ago
Add or subtract a user-entered number from each selected track's Plays
downloaded 1h 25m 32s ago
Export artwork of selected tracks to parent or specified folder
downloaded 1h 30m 6s ago
Set the Plays of selected tracks.