Oli Larkin has released Beat morpher, which is a sample playback VST drum machine for Windows "with a difference".

You specify start and end positions for each drum hit, then you can morph between the two patterns using a slider or by just pressing the auto-morph button - the beat will gradually morph over a specified number of bars.

This effect was inspired by the music of Simon Posford aka Hallucinogen and Shpongle (with raja ram).