Below is a sample WebM video encoded with Wildform Flix which is a FREE WebM encoder. You need a HTML5 enabled browser and browsers that support WebM videos.
And while at it, why not read WebM Overview.
Which browser can see this video?
You can use the The latest build of Chrome to view the video.
The video is (c) copyright 2008, Blender Foundation / www.bigbuckbunny.org.
Visit Big Buck Bunny at http://www.bigbuckbunny.org/
Click here to see another sample WebM video.