V8 is written in C++ and is used in Google Chrome, the open source browser from Google.
V8 implements ECMAScript as specified in ECMA-262, 3rd edition, and runs on Windows XP and Vista, Mac OS X 10.5 (Leopard), and Linux systems that use IA-32 or ARM processors.
V8 can run standalone, or can be embedded into any C++ application. http://code.google.com/p/v8/
Gears is an open source project that enables more powerful web applications, by adding new features to web browsers.http://code.google.com/p/gears/