I consider the big Wohoo in the title valid here! The NoMoreiTunes Extension for Safari 5 puts an end to something that I have been annoyed at ever since the wonderful iTunes Preview was announced.
Short back story. Nowadays when you click on an iTunes link, you get a nice web interface, showing the same information as it would once it has opened in iTunes. Sadly, what it also does is force iTunes to open and open the same information in the iTunes Store, there.
This extension does one thing. Stops iTunes from opening when you click an iTunes link, allowing you to use the iTunes Preview interface on the web instead of being forced into iTunes.
The extension is free and available for download.