http://www.spotify.com/
Spotify is a subscription based music streaming service based in Europe. Available in the UK for £5 to £10 a month.
http://symbianoggplay.sourceforge.net/
Open source media player (supports mp3, ogg, and more) for Symbian devices. Great for the E51, much better than the in-built player. Supports skip forward / back... :-)
http://www.rockbox.org/twiki/bin/view/Main/DocsIndex
Rockbox, alternative firmware for ipods and other digital music players
