Mastervst.com has released Grasshopper, a freeware pattern generator VSTi.
Grasshopper allows you to load wave files and automatically generate rhythmic patterns based on parameters you set. Grasshopper comes with 21 drum samples to get you started.
Note: When loading the VSTi it might complain about not finding the samples. It seems the samples path is set to the one the developer used, so just reload the samples (or your own).
Visit Mastervst.com for more information.