There is a program called
Re-Cycle (originally for the
Atari ST, now for the
PC and
Mac) which virtually invented the modern breakbeat, especially in the manic cut'n'paste form heard in much
drum & bass music.
When fed a sample, it automatically detects the beats within it and cuts it into as many separate smaller samples as you require, which you can then transmit (via midi or scsi) back to your hardware sampler or load into your appropriate software.
The real magic of the program is that is also generates you a midi file which, when played into the sampler will recreate your original loop, or, more usefully, allows you to have enormous fun cutting up and changing the original loop into something far more crazed and frenzied.