A lot of people are wondering if .NET 3.0 is a new version of .NET, and if they'll have to port their application from .NET 2.0.

Actually .NET 3.0 is a bunch of new things (WPF, WCF, WCS and WF) built ON TOP OF .NET 2.0. So anything you've built with .NET 2.0 will run normally on .NET 3.0.