On September 4th, 2007 9 PM PST Microsoft released to web (RTW) Silverlight 1.0 and announced that they will work together with Novell Inc. to enable silverliht applications on Linux.

ScottGu posted what's in silverlight 1.0 release:

  • Built-in codec support for playing VC-1 and WMV video, and MP3 and WMA audio within a browser.  The VC-1 codec is a big step forward for incorporating media within a web experience - since it supports very efficiently playing high-quality, high definition video in the browser.  It is a standards-based media format that is implemented in all HD-DVD and Blueray DVD players, and is supported by hundreds of millions of mobile devices, XBOX 360s, PlayStation 3s, and Windows Media Centers (enabling you to encode content once and run it on all of these devices + Silverlight unmodified).  It enables you to use a huge library of existing video content and provides access to the broad ecosystem of existing Windows Media tools, components, vendors and hardware. 
  • Silverlight supports the ability to progressively download and play media content from any web-server.  You can point Silverlight at any URL containing video/audio media content, and it will download it and enable you to play it within the browser.  No special server software is required, and Silverlight can work with any web-server (including Apache on Linux).  We'll also be releasing an IIS 7.0 media pack that enables rich bandwidth throttling features that you can enable on your web-server for free.
  • Silverlight also optionally supports built-in media streaming.  This enables you to use a streaming server like Windows Media Server on the backend to efficiently stream video/audio (note: Windows Media Server is a free product that runs on Windows Server).  Streaming brings some significant benefits in that: 1) it can improve the end-user's experience when they seek around in a large video stream, and 2) it can dramatically lower your bandwidth costs. 

  • Silverlight enables you to create rich UI and animations, and blend vector graphics with HTML to create compelling content experiences.  It supports a Javascript programming model to develop these.  One benefit of this is that it makes it really easy to integrate these experiences within AJAX web-pages (since you can write Javascript code to update both the HTML and XAML elements together). 

  • Silverlight makes it easy to build rich video player interactive experiences.  You can blend together its media capabilities with the vector graphic support to create any type of media playing experience you want.  Silverlight includes the ability to "go full screen" to create a completely immersive experience, as well as to overlay menus/content/controls/text directly on top of running video content (allowing you to enable DVD like experiences).  Silverlight also provides the ability to resize running video on the fly without requiring the video stream to be stopped or restarted.

There is another RTW Expression Encoder 1.0 release on the web.  Expression Encoder is part of the Microsoft Expression suite of products, and enables designers and content professionals to enhance, encode and publish media content for Silverlight.  You can use it to import media files from a variety of formats (QuickTime, WMV, AVI and more), add leaders and trailers to videos for advertising or roll credits, easily watermark video with corporate logos or brands, and then tune the encoding settings to create optimal web-friendly Silverlight experiences.

Silverlight is used on several MS sites - MSN Podium '08, Halo 3 HD Preview...

Here are some screenshots: