According to the folks of /. (SlashDot), Google is preparing the launch of their own browser, Gbrowser. Evidence include the registration of the gbrowser.com (currently not in use) domain name by Google and the fact that they hired several developers recently.
According to evidence in Mozilla’s Bugzilla, the browser might be based on the Gecko rendering engine

Update:

More information can be found here:

More evidence of a Google browser

The Google Browser

Google picks Gates’ brains

Google Browser?

The Google Browser