InfoWorld has a really good review of Silverlight, the RIA competitor to Flash/Flex.

I think Silverlight may make a big splash as most .NET developers are probably "graphically challenged" and Silverlight will allow them to create slick RIA's in a familiar environment (Visual Studio) and language (C#, Visual Basic .Net, IronPython, and eventually IronRuby).

Microsoft also released a beta of Popfly, their hosted mashup builder. The UI has been cleaned up quite a bit and they now offer integration with Visual Studio and Visual Studio Express that allows you to build mashups in an environment that developers are familiar with. One issue I have with the service is that the Silverlight components are hosted but they announced functionality to download mashups as gadgets for Windows Sidebar. No way to upload your mashups to your own server.

On the other hand, Flex has a little steeper learning curve if you are not already familiar with Flash or are not a designer. You not only have to learn MXML but the real power is in the ActionScript language.