You can make a copy of it, put both copies in iTunes, hit get info on them, and change their start and end times.
For example, say you have a 30 minute song, but you want to break it into two songs that are 14 and 16 minutes long. You duplicate the file and import both into iTunes. You then set one copy to have the start time of 00:00 and the end time of 14:00. Then you set the other to have the times 14:00 and 30:00. If you need to break it into more than two parts, just make more copies of the original and adjust their start and end times accordingly.
I use Audacity in combination with the LAME codec to chop up talk shows so it's easier to find my place again when I'm out and about. My MP3 player does have a pause function, but files can easily become 'unpaused' when you do other things (like recording) in between listening to shows. The fast forward is so slow it can takes ages to 'wind' a track to, for example, the 60 minutes point. I wish I could select the position I wanted to jump to and then just press play.
Anyway, Audacity is simple and free, I can't fault it. A good tip if your MP3 player can record from the radio or another source is to stop and start it again at regular intervals to break up the audio into more manageable segments.