I have been using this little stand-alone. It works well for me, and it is free. There is a limit of the size the free will work with. I have Fog Hat--Slow Ride (full studio) 7.53mb that is 116% too big for the free version. You can register to get additional file size support for a price.

http://www.logiccell.com/~mp3trim/mp3trim.htm