OggPlay

Audio Player for Symbian OS
OggPlay is an audio player for smartphones. OggPlay was initially written for SonyEriccson P800 and then released under the GPL by Leif H. Wilden. In a true open source project, OggPlay has been since ported to several Symbian phones.
Main features of OggPlay:

• Plays .ogg audio files
• Detects and plays audio format supported the phone (MP3, AAC, MP4,M4A)
• Free!
• Skins (you can make your own, or use already made ones)
• User defined hotkeys
• Autoplay

Features supported varies a lot depending on the phone OggPlay is installed on.
OggPlay is ported on Series60, Series80 and UIQ.

For converting your MP3 music collection to the much better and smaller Ogg Vorbis you can use:
dBpowerAMP Music Converter
and then transfer them to your phone using a Card Reader or a Bluetooth PC Connection. I suggest using a 64kbps for Ogg Vorbis to equal the quality of a 128kbps MP3.

You can download OggPlay and Skins here:
symbianoggplay.sourceforge.net