skiTunes is a fast, extensible alternative to iTunes. It can use Apple Quicktime, VLC, MPlayer, LAME, and cdrecord. It differs from Apple's offering in that it is written in Cocoa and uses native widgets, as well as supporting formats iTunes doesn't, such as OGG and WMA. Using native widgets will allow it to automatically match the rest of the OS when a theme is applied, unlike iTunes, which requires hacking in order to make it match. It will also offer a skinnable "mini- mode".
BackPlay a program that plays music files from a folder in the background. At login, it scans a directory called "BackPlay" under the user's Music directory, and begins playing any music files it finds there in random order. BackPlay is independent from iTunes. It can be paused from an icon in the status area.