It was surprisingly easy to learn. I picked up most in a few days - its the tweaking that is a great deal harder. You can do so many things in it without the Tweaking but for power you need to know Visual Basic or C#; the languages which ASP.NET will take and make it more powerful and durable than PHP is. Some of the things you can do on Websites with the power of Application Programming Languages is quite generally amazing.

Best thing you could do to begin to pick it up is get the Visual Studio 2005 Beta 1 Version. It comes with MSDN Library 2005 on the Download, SQL Server 2005 Beta 2; and all the tools you'll need to get along with any Books, or just fiddle about.

I personally read Dino Esposito's Introduction to ASP.NET 2.0 from Microsoft Press; it was great and more than enough to get you into the basics and off thinking about all the things you can do.