I've been looking for a lightweight mp3 player that makes it easy to modify tags, search through thousands of tracks for precisely the song I want, and offers useful options to help build playlists catering to the mood that I in at a particular time. MusikCube is close. Last time I tried it, it still had a number of bugs that kept me using WinAmp. Hopefully they have been fixed. Here is a link and a screenshot.