Other than MP3, What Compressed Audio Formats Exist?

cd asks: "While the MP3 format has become the dominant form for compressed music on the Internet, is it the most technically superior? What other forms of music compression are available for those who don't wish to download new music or upload their music, but for those who simply want to archive their music CDs? In this article Ken Thompson mentions PAC format. Is this the way to go? Is their encoding and playback software available for Linux?"