From University of California, Irvine:

VATIC is a free, online, interactive video annotation tool for computer vision research that crowdsources work to Amazon's Mechanical Turk. Our tool makes it easy to build massive, affordable video data sets and can be deployed on a cloud. After three years of research, vatic is now used by labs around the world to annotate the next generation of data sets.

Features

• Crowdsource video annotation to Mechanical Turk
• Automatic quality assurance for good annotations
• Complex payment schedules and bonuses
• One-click worker compensation
• Optimized interface for video annotation
• Offline mode for expert annotator use (no MTurk)

(site) (github)