MPoD is your iPhone / iPod Touch remote control for MPD (Music Player Daemon). Featuring a slick, intuitive user interface, MPoD makes it very easy to browse through your collection, and play the music you want to hear from a large collections of artists, albums and songs.
Note that MPoD is not a stand-alone application: it will only work in combination with MPD, and it doesn't play music on your iPhone. If you don't have an MPD server running in your home (which usually runs on Linux) then MPoD will not provide any value to you.
You can find details on MPD at http://www.musicpd.org.