More than another web-based video tool with a stupid name, Omnisio enables users to:

• select clips from YouTube and other video service
• embed comments in the video
• assemble your own video compilations from edits you've made
• sync a video to a PowerPoint slideshow
• chapterize a video

Updated: It appears that Omnisio has been bought by Google. Much of the functionality in the site has been disabled, but we might start seeing more Omnisio-like annotation in Google Video soon.