Download it. 1.1 megabytes, Windows 2000 or higher, Firefox 1.0 or IE 5.0 or higher. If you’d like, get the source code.
Additions to the Google Video FAQ:
Most recently, we have increased our video library to include all types of video content uploaded from a variety of video publishers and allow you to play them back for free. See some samples of these videos.
What does the triangle icon next to the snippets mean in the search results?
The triangle icon means a video is available for playback for free.
Can I play the videos that Google Video finds?
Some of the videos are only still images while others allow playback. Videos that offer playback will be labeled with a triangle play icon in the search result.
How do I playback video?
In order to playback video on Google Video, you first need to install the Google Video Viewer (Videolan 0.8.1). Once installed, you will be able to playback the video from within your browser. This viewer will not interfere with the other video players on your system.
For non-televised videos, we search based on descriptive text (geeks call this “metadata”) provided by the content owners. Thus, the quality of text returned on the re su lts page is dependent on the content owner.
Why are the videos sometimes grainy? Why is the sound quality inconsistent?
We simply index what content owners upload and have no control over the quality and sound of the resulting content.
How do I uninstall the Google Video Viewer for Windows?
You can remove the Google Video Viewer by using the Windows “Add/Remove Programs” control panel.
I guess all that’s left is to find some cool videos. Just look for the 
UPDATE: Chris Sherman at Search Engine Watch has a nice long article on the release, with a few more details:
Video clips will begin playing from the point where your search terms are found in the audio portion of the video. If your search terms appear in multiple locations, results will display thumbnail stills and snippets from those locations, as well.
To watch some video programming, you’ll have to pay a fee. In most cases, this fee was specified by the content owner, not Google, though Google takes a small portion of the fee to defray its costs. The exception is if Google’s costs are extraordinary-say for a popular, high resolution video. In that case, Google may arbitrarily charge users a fee if you’ve specified zero as the price for your video or take a larger revenue share of the price to cover some of these costs.
Google Video search looks at metadata encoded with the video. [Google senior product manager Peter] Chane said many videos were also submitted with transcripts and annotations that are time-coded, allowing playback to begin at the point where your search terms are located in clips.
Links:
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source code
Nathan Weinberg writes the popular InsideGoogle blog, offering the latest news and insights about Google and search engines.
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