Solved some WCF + Windows Server 2008 problems today and the following links helped me :

1. Don't forget that WCF is a feature-> read this to activate it in ws2008.
2. Using WCF with WAS in Windows Server 2008 (a bit easier than with Vista)

I just spent a couple of days with Silverlight v2:

• 1.Silverlight 2 beta 1 (Scott Guthrie tutorial)
• 2.Blend 2.5 beta (Scott Guthrie tutorial)
• 3.Sharepoint + Silverlight (+ on Windows Server 2008 which is my "normal platform")

For Silverlight 2 & Sharepoint, if you don't want to waste one day or more, just follow Patrick's instructions to modify the web.config file (+Mime)  and don't forget to recompile your "SL.XAML.HelloSilverlight2 project". Let's repeat it : "recompile you xap project, dude".