The Unity Web Player enables you to view blazing 3D content created with Unity directly in your browser, and autoupdates as necessary.
Unity allows you to build rich 3D games with animated characters, sizzling graphics, immersive physics. Then you can deliver the games to the web or as standalone players.
Unity Web Player for Windows
Internet Explorer, Firefox, Chrome, Safari, Opera
Requirements
Windows 2000/XP/Vista/7
http://unity3d.com/webplayer/