There's no good, WinAmp-style mp3 player for Symbian S60. I tried about all of them, and none of them was good. 
Deal breakers indicated with a *.
The winners: Nokia's built-in player, tamed with this 
folder structure workaround, and 
PowerMP3. Which one works best depends on which version of Nokia's player came with your phone. Runners-up: 
TTPod and LCG Jukebox. All the other music players for Symbian are a waste of time.
updated May 6, 2009Nokia's built-in player€0 (hidden in price of phone)
* Music Library only displays track title. No option to display tracks as artist-title or by file name, which makes navigation of large music collections unnecessarily complicated.
* Music Library ignores folder structure, which makes navigation of large music collections unnecessarily complicated. 
Workaround: copy the folder name to the composer field of the mp3 tags.* Music Library is unable to ignore ringtone folder(s).
* Some versions of Nokia's music player don't have a "now playing" list. And those versions that have one can't append tracks to it. Selecting a new track or group of tracks overwrites the current list. (workaround: create a temporary ad hoc playlist)
* Playing a song automatically adds the entire virtual folder (artist, album, genre) to the "now playing" list instead of just the selected track.
- Opening a track from the file manager launches the player in reduced functionality mode.
- Player stores playlists in the root of the phone memory or memory card instead of in a user-defined folder.
ALON MP3 PlayerUS$20
* No version for S60 v3 available (yet).
CorePlayerUS$25
- Player running in the background doesn't show anything on the standby screen.
* Program crashed when I tried to play an m3u playlist.
* Navigation by folders, but not by mp3 tags like artist or genre.
CubiX MP3 PlayerUS$12
* No version for S60 v3 available (yet).
EzPlayUS$5
* No version for S60 v3 available (yet).
FIVN Player€6
* Lengthy search for tracks everytime you start the program.
* Displays all tracks in one giant, non-searchable list, which makes navigation of large music collections impossible. No ordering by genre or artist, completely ignores folder structure or mp3 tags.
- Player running in the background doesn't show anything on the standby screen.
* Player window doesn't indicate which track is playing.
* Doesn't support playlists.
* Can only play all tracks in alphabetical or random order. Can not play a selection of tracks, can not play tracks in user-defined order.
GlassPlayer€3
* Endless requests to permit reading user data on phones that don't have an "always allow" setting.
* Refused to add any tracks to playlist.
* Refused to play any tracks.
Handy Musicfree
* Shows all your songs in one big list which can't be searched. Useless for large music collections.
* Ignores folder structure and mp3 tags.
KD Playerfree
* Refused to add tracks to library.
LCG JukeboxUS$25
- Lyrics viewer doesn't see lyrics stored in IDv2 tags.
- Player running in background shows on standby screen, but can't be controlled or launched from the standby screen.
- Closing the player from the exit softkey launches an "are you sure?" dialog which can not be switched off.
* No navigation by tags like artist or genre, only by folders.
LyricsPlayerfree
* Program extremely slow.
* No sound at all.
* Endless requests to permit reading user data on phones that don't have an "always allow" setting.
MMPlayerUS$18
- Player running in the background doesn't show anything on the standby screen.
* Doesn't support .m3u playlists.
- Hard to navigate user interface.
* No navigation by tags like artist or genre, only by folders.
Mobile Media Playerfree?
* No version for S60 v3 available (yet).
Mobiola Media PlayerUS$15
* No version for S60 v3 available (yet).
moremediaUS$10
* No version for S60 v3 available (yet).
MP3 BASE-STEREO-EQUS$15
* No version for S60 v3 available (yet).
MP3GoUS$45
* No version for S60 v3 available (yet).
MP3 Gravity€13
* No version for S60 v3 available (yet).
MP3 Music Box by Spinlet* No version for S60 v3 available (yet).
MSI Blue Player?
* Doesn't play anything without bluetooth devices.
muzeeUS$15
* Doesn't support playlists.
* Couldn't test the program because it kept crashing.
MyStrands Social Playerfree
- Player running in the background doesn't show anything on the standby screen.
* Music Library ("My Music") ignores folder structure, which makes navigation of large music collections unnecessarily complicated.
* There's a "Playlists" entry in the "My Music" panel, but it didn't work with my m3u playlists.
* Plays all selected tracks in alphabetical or random order, but not in user-defined order.
OggPlayfree
- Installation is a mess. Expired certificate, needs special skin to work on most phones.
- Can't make playlists from within OggPlay.
- Player running in the background doesn't show anything on the standby screen.
* Ignores the volume rocker.
* Lists of tracks, artists etc. can only be scrolled, not searched. Can't scroll lists of tracks, artists etc. by keeping the navigation button pressed. Scrolling requires a single keypress for each and every line, which makes large music collections impossible to navigate.
PowerMP3free (beta test version)
* Music Library only displays track title. No option to display tracks as artist-title or by file name, which makes navigation of large music collections unnecessarily complicated.
* PowerMP3 gets the sort order of m3u playlists wrong if the lists were made or edited with other programs (such as WinAmp or Symbian's built-in music player), and songs with characters like ã, ç, and é won't show up in the playlists at all. And if you edit a playlist with another program, PowerMP3 won't pick up the changes. 
- Player running in the background doesn't show anything on the standby screen.
- Sorts music by mp3 tags artist, album, and genre, but not by composer.
- Beta test version.
RealPlayer for Mobilefree
* No version for S60 v3 available (yet).
S+Amp Music playerfree
- Player running in the background doesn't show anything on the standby screen.
* Ignores the volume rocker.
* Doesn't support playlists.
* Displays all tracks in one giant, non-searchable list, which makes navigation of large music collections impossible. No ordering by genre or artist, completely ignores folder structure or mp3 tags.
Telstra Music Playerfree (not available for non-telstra customers)
- Player running in the background doesn't show anything on the standby screen.
* Ignores the volume rocker.
* Displays all tracks in one giant list which makes navigation of large music collections impossible. No ordering by genre or artist, completely ignores folder structure or mp3 tags.
TTMusicfree
* Program crashed on launch.
TTPodfree
- Active Standby screen mini player doesn't work.
* Doesn't support m3u playlists.
* No ordering by genre or artist, ignores mp3 tags (even though it has an mp3 tag editor).
UltraMP3€5
* No version for S60 v3 available.
Viking Mp3Player€10
* After installation the program did not appear in the applications manager of my phone.
- Player running in the background doesn't show anything on the standby screen.
* Doesn't support playlists.
* No ordering by genre or artist, completely ignores mp3 tags. Doesn't display subfolders as subfolders.
* Slow menus.