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 better (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.
(Note: In order to launch this PowerPC-era script on an Intel machine, it must first be opened and then saved using AppleScript Editor, which is located in your /Applications/Utilities/ folder. More information is here.)
Two scripts copy text from the clipboard to current or to selected track's lyrics
Update subscriptions which have expired by virtue of being ignored for five or more days
Sort purchased tracks into discrete playlists by name or account ID
Set the Plays of selected tracks.
App displays files in iTunes Music folder which are not in iTunes library
Copy number prefix in Song Name of selected tracks to their track number tag