Being able to trick out my browser is one of the reasons I love Firefox. Being able to trick Firefox out with music extensions makes me love it unconditionally.
Fire FM adds a skinny little bar to Firefox, and then boo-ya, you've gotten access to Last FM's entire library of music. Just go to the bar, select a station or an artist station, and get groovin'. Anything that lets me rock out with as little effort as possible has a fan in me.