As of a short while ago, Visual Studio 2008 Beta 2 was released. This also includes the .NET Framework 3.5 Beta 2. Silverlight 1.0 RC is expected to be released within the next couple of days.
Also, these releases (Visual Studio 2008 Beta 2, .NET Framework 3.5 Beta 2, as well as Silverlight 1.0 RC) come with a "go live" license that allows you to start development now and not have to worry about a supported upgrade path when the final versions ship later this year.
Here's a list of the installation disc images that can be downloaded:
Also, there are a couple of VPC images that can be downloaded as well:
The Visual Studio Express Editions can be downloaded from here.
The Microsoft .NET Framework 3.5 Beta 2 can be downloaded from here.