If you only need something to play music/video files, I would suggest VLC Player; I haven't found anything better. However, if you're big into organizing your music (different playlists for different moods, etc.), you might find VLC to be lacking a bit.
One of the reasons I enjoy iTunes is that I'm not big into organizing my music and playlists-- iTunes does it for me. Will VLC move my music into an organized directory and let me play an album, or shuffle through all songs from an artist or genre without me having to create playlists?
Check out Ecoute. A gorgeous UI "designed to be minimal, small and pretty so it doesn't take a lot of space on your screen. Just what you need to play your library."
