Viddler : Enhance and Share your Videos

Viddler is a video editing and sharing website with an excellent additional feature that enables users to comment on and tag specific moments in the video.

Viddler Overview

Upload and Share videos: Supports most of the video formats: .mov, .avi, .wmv, AND .mpeg. Note: max. video size is limited to 500 MB.
Add timed Tags: tag particular moments on the video timeline. Timed tags are searchable.
Add timed Comments: comment on and discuss specific moments on the video.
Option to upload live footage from your camera directly to your Viddler account
Embed Viddler videos anywhere on the web. (see below)
Explore Viddler videos by: popularity, tags, users, and more.

Viddler video (demo):

Viddler Review (by 1938media):