My new HTC TyTN is able to use any MP3 as ringtone but an MP3 version of a three minute song can easily take up 3 MB of storage. This is overkill because a nice 15 second loop will sound just as good and takes only 200 KB.
But how do you get 15 seconds out of a 3 minute song?
Audacity, a free sound editor, comes to the rescue. It allows you to cut a piece out of an MP3 file, and apply effects to Fade In, Fade Out or Amplify the sound. After saving the edited sound file as an MP3 (with some help of the LAME MP3 encoder) you can put it on the TyTN using ActiveSync and use it as a ringtone.