Today, we launched Google Chrome's extensions system in the beta channel for Windows and Linux (Mac is in progress).

Google is getting into the operating system business (again) with Google Chrome OS. Palm put WebKit at the heart of a device with webOS, the Crunchpad talked about it for the netbook, and there have long been desktop-boot-to-browser devices out there.
Google Chrome OS goes deeper:

The Google Client Team had an exciting and inspiring two days last week at Google I/O. We had the opportunity to talk to developers and have insightful conversations on what we're doing in the realm of HTML 5, Chrome, V8, Native Client, and 3D graphics on the web.