Last.wp is a WordPress widget that shows your guests what you've been listening to on Last.fm, via a jQuery plugin!
On the technical side, Last.wp is powered by a small plugin provided by the kind people over at Engage Interactive. (Thanks for providing it under the GPL guys!). Unfortunatly, it requires each person to have their own API key as of now, due to Last.fm's confusing API system. It's easy to get one, you just login and go to the API screen, create a new application, and Voila, your very own API key! (Consult the Instructions for details)