Prosecutor Bob McCulloch announced the grand jury's decision.

On Monday night, St. Louis County prosecutor Bob McCulloch announced that a grand jury had decided not to charge Ferguson, Missouri, police officer Darren Wilson with a crime for killing 18-year-old Michael Brown in August.
County officials distributed documents from the grand jury deliberations to the press. St. Louis Public Radio has been uploading and posting the documents, which you can sift through here.

But if you're looking for the major documents, here are links to some of the key information from the case:
Michael Brown's official autopsy report
Investigators' interview with Darren Wilson

Darren Wilson's medical examination after killing Michael Brown
Crime-scene analysis of firearm evidence