StumbleUpon, makers of the popular toolbar for using collaborative serendipity to find web sites, is applying its model to online video. We think “stumbling” actually works better for video, where it is hard to find new and interesting stuff. We actually surf for video — happy to find random, unexpected, entertaining clips — whereas on the web we are more directed.

After seeing users migrate to an option that allowed them to stumble specifically for videos, StumbleUpon created a video-specific tool, launched late Wednesday night. The advantages: an AJAX-driven browser-based service that doesn’t require registration (as opposed to the company’s core webpage discovery service, with requires both download and user IDs), and automated formatting for a consistent experience for clips from YouTube, Google Video, and MySpace.

The result: an in-browser television of sorts, which you can sort by category, and which learns from your ratings if you register. It also has nice keyboard shortcuts for moving on to the next video, and giving videos a thumbs up or thumbs down. The program keeps a record of what you’ve seen and what you liked, so it’s essentially an automated bookmarking system.

StumbleUpon proper claims 1.6 million members, 600,000 of them active per month. The company sees 4 million stumbles per day via its toolbar, of 7.5 million URLs in its database.

StumbleVideo currently does not feature any advertising, which is StumbleUpon’s business model. StumbleUpon CEO Garrett Camp says the company is seeing strong revenue from its core product, but it may raise another venture round early next year.

StumbleUpon is the first company to be featured in what we hope to be a regular feature on web video curators.