All you do is control-click the mp3 you want to split, then click 'get info', and then click the 'options' tab. check the start and end time boxes, and put in the times at either end of the bit you want to cut out, then click OK. go to Advanced and click 'convert selection to MP3', and itunes makes a new mp3 with the bit you want. it doesn't do anything to the old mp3, but don't forget to go back in and uncheck the start and end time boxes if you want to listen to it normally again.
this is great for cutting out secret tracks, or in my case, pulling apart a whole album mp3 so i can burn it in tracks. and it's a hell of a lot faster than doing it in Quicktime Pro (which i don't have anyhow).
*headbobs happily to newly-titled mp3s*
does eating bananas make anybody else hungrier than when they started?