WebM Inline Player replaces links to WebM files with embedded videos, so you can watch them without leaving the page. It works almost on any website.

Key features:

• 3 methods of starting video playback: on mouse click, on mouseover and automatically on scroll (one video at a time - it won't burn your CPU)
• Ability to mute all WebM videos by default
• Ability to specify the maximum size of the video player

You can test this extension here: http://webmtest.tumblr.com

Also available as an extension for:
Firefox
Chrome
Opera

Options: