This script will examine the current web page in Safari for your choice of media file links (currently mp3, aac, and pdf files) and allow you to select any found files to download and then add them to iTunes. Options include selecting download location, adding to a particular iTunes playlist, and the ability to delete the original files after adding to iTunes. Be sure to read the Read Me.
DISCLAIMER: This script is not intended to be used to download copyrighted material. Please bear that in mind.
(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.)