I've got a Nokia 6681. I've removed a lot of bloatware from it - all kinds of 'movie editing' and 'office' junk.
The only additional piece of software I've installed in it is OggPlay (
Symbian OggPlay). I've got about 310 ogg music files, some of which have runtimes of over 20 minutes, on my 512MB RS-MMC. I couldn't have had so many mp3 files on a 512MB card without sacrificing on audio quality. Oggplay rules.
