So, fresh from the bowels of http://del.icio.us/popular/ comes this fantastic link:
FoxiPod

What is FoxiPod, you might ask? It delivers basically an almost perfectly ideal experience: Any .mp3 file linked on a website (such as on an .mp3 blog for example) gets a little icon beside it. Click the icon. The mp3 gets downloaded into itunes. Which will then synch it to your iPod. FREAKING AWESOME!

FoxiPod

FoxiPod uses Greasemonkey with Firefox to make downloading MP3s and music files and adding them to iTunes a single-click process.

Go get it now. And, well, sorry Windows-only users. This is Mac only. Gaaaaaaa! 🙂