Acid Pro: Loop based music creation tool.
Atomix Productions: Offers Virtual DJ, DJ Box, and AtomixMP3 programs.
eJay: Music creation using DJ samples. Artist forums, net radio available.
Hip Hop Starz: Make your own Rap and Hip Hop. 1100 samples and loops for constructing your tracks.
Jackson, DJ: Mix any style of music and change the structure of songs while you're playing them.
Magix Music Maker: Sample based music creation, also templates for making musical websites and videos.
Samplisizer: Create music in modern club styles. Demo available.