Microsoft Tuesday released the final version of Silverlight, a new browser plug-in supporting streaming audio, video and graphics.

Silverlight is Microsoft’s direct response to Adobe Flash, which is the dominant vehicle for delivering animation and video on the Web. In addition to offering a browser plug-in, Silverlight includes tools for enabling developers to create interactive, browser-based applications.

Microsoft has had success with its Windows Media technologies, but Silverlight is focused on delivering a cross-platform experience—important if Microsoft is to reach beyond its base of Windows users. In its 1.0 version, Silverlight works on Windows and Apple platforms. Microsoft also announced that it is working with Novell to deliver Silverlight support for Linux systems—dubbed “Project Moonlight.”

In addition to the challenge of supporting non-Windows platforms, Microsoft faces an uphill battle getting Silverlight available as widely as the competing Flash, which by Adobe’s estimates is installed in well over 90% of all Web browsers. For Web content, the bigger the installed base, the more likely developers are to create content specifically for a particular technology.

A good example of a Silverlight application is MLB.com’s game-casts, which include video streams and interactive graphics. That application was the first public Silverlight app to hit the Web earlier this summer.

Microsoft this week announced additional Silverlight content partners—including Entertainment Tonight, HSN and World Wrestling Entertainment—along with a Silverlight Partner Initiative that includes 35 content development firms.

The free Silverlight browser plug can be downloaded at www.silverlight.net.