xnoise is my pet project.
xnoise is a gtk+ media player using the gstreamer framework. Unlike rhythmbox, banshee or itunes, it uses a collection-tracklist concept.
It is written in vala. That means, it is compiled to GObject/C and is therefore lightweight and fast (no python, no mono).
It uses a sqlite database, plugins and a lot of drag'n'drop.
More info on the project's homepage: