Silverlight is a cross-browser, cross-platform plug-in for delivering the next generation of media experiences and rich interactive applications (RIAs) for the Web. Silverlight 1.0 will auto-update to the final release. Operating System: Windows Vista, XP, 2000, 2003, Mac OS 10.4.8+ (PowerP & Intel-based). Browsers: Windows Internet Explorer 6 - 7, Firefox 1.5 - 2, Safari. Free. No limitations. Microsoft Silverlight 1.0 will auto-update to the final release.