As a related project to the VP8/Webm video codec, Google has released an early version WebP (goo.gl/VmXd), of a lossy image compression that claims to have better compression results than JPEG (goo.gl/7an8).
There is no patent incumberance of this file format.
Google has also announced to add WebP support to its Chrome Browser and to submit a patch to the Webkit rendering engine. The relationship of WebP and WebM means that a browser already using libvpx for the video display will have little problems adding support to the webp images and support for webp by Firefox and Opera is likely.
.webp should be added to the permitted file extensions for Wikimedia Commons uploads, even if right now webp files should not be included for example for the illustration of Wikipedia articles.