The creators of
Gigastudio and its precursor
Gigasampler, which are
software samplers that
stream audio information directly from the
disk to the soundcard. For an explanation of why this is cool, see the
gigastudio writeup.
Nemesys music started out pretty small and their first product was fairly revolutionary in the world of sampled instruments. They have since been purchased by TASCAM, a much larger company with a long history of good music products.