It’s a useful little tool on it’s own, you can read more about it here on their official website or over here at FireFox Add-ons.
Anyway, for people already using FoxyTunes or anyone who is now interested you make want to check out their new beta Foxy Tunes Planet. It’s a private beta and numbers are limited, so get in soon if you want to take part.
Standard FoxyTunes works with FireFox & ThunderBird. The new beta software will work with both FireFox and Internet Explorer. I got accepted to be apart of the beta earlier today and my first impressions of the site is it's actually pretty cool, here’s a couple of screen caps:



In the first screen cap I've circled normal FoxyTunes so you can get an idea what it looks like, and the pop-up info for the track I was listening to can be seen in the third.