UPDATED: Save Album Art to Album Folder v4.0
Save Album Art to Album Folder v4.0 is a script that will export the artwork data of the selected tracks or tracks in the selected playlist as an image file to the folder which contains each selected track's filepresumably the track's Album folderor a specific user-selected folder. Additionally, you can customize various settings for the image file:
This latest version is a Cocoa-AppleScript Applet, so it can only be run on OS X 10.6 and 10.7.