At Mix '07 this week there were some interesting relseases and demos - one spefically is Silverlight - that is cross-platform - with releases available on Windows and Mac OS. There is also a Silverlight Community site available with some examples - like the Fox Movie trailers...they looked great fullscrean on my large monitor.
Microsoft® Silverlight™ is a cross-browser, cross-platform plug-in for delivering the next generation of .NET based media experiences and rich interactive applications for the Web. Silverlight offers a flexible programming model that supports AJAX, VB, C#, Python, and Ruby, and integrates with existing Web applications. Silverlight supports fast, cost-effective delivery of high-quality video to all major browsers running on the Mac OS or Windows.