This is probably the most useful command when it comes to splitting large mp3 files. You'll need mp3splt (http://mp3splt.sourceforge.net) and you're ready to go:
mp3splt -s -p th=-40,min=6,rm
Parameters explanation:
'-s': silence mode; activate silence detection
'-p': specify arguments for the silence mode
'th=-40': threshold level (dB) to be considered silence
'min=6': minimum number of seconds to be considered as splitpoint
* 'rm': remove silence from splitted files
Be sure to have a look at the manpage. Happy splitting!