oh, sorry, no, what you do is download the last.fm plugin, which will install to your itunes and will scrobble everything you listen to so that it shows up on your last.fm profile. you can also download the last.fm app if you listen to music via your phone which will do the same thing there, and if you use Spotify there’s an option in Settings to enter your last.fm login and it will track from there too.
it’s a bit unclear since they launched a massively unfinished website design a while ago with lots of things missing (though they’re coming back gradually) and i think the download page for the plugin has disappeared and i need to have a hunt for it for you.
no worries about the mix, you’re not one of my recipients but i haven’t sent any of mine yet either. d’oh.