Windows 8 and Metro are new to most developers. Luckily, the
//build/ event has a TON of great sessions explaining how to get
productive with the new development stack. Here's my personal list
of Build 2011 videos that XAML developers (Silverlight, WPF, Phone)
should see, roughly in order starting with key Windows 8
sessions.
The video player supports trick play (on IE9, right-click and
set the play speed), so after the first two sessions, play the rest
at 1.4x to get the most out of them in the least amount of
time.
In time for your weekend downtime and your flights home, here's
my list of must-see sessions.
Day 1 Keynote with Steven Sinofsky
If you want the big overview of Windows 8 and Metro, this is the
session to watch. This is probably one of the best keynotes I've
seen.
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8 Traits of Great Metro Style Apps with Jensen Harris
If you want to learn "Why Metro" or how the Windows 8 Metro UI
works, watch this. Jensen does a great job making the design
accessible to everyone while laying all the cards on the table.
After watching this, if you want more designer-oriented
information, check out Designing Metro style: principles and
personalities.
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Platform for Metro-Style Apps with Ales Holecek and John
Sheehan
A great overview of the platform, Windows RT and Windows 8
itself. If you want to know more about the API, this is the
session. Lots of C++/XAML love in here too.

Tools for Building Metro-Style apps with Chris Sells and Kieran
Mockford
This is the second part of the Platform talk

Lap around the Windows Runtime with Martyn Lovell
This gives you a deeper look at WinRT

Metro-style apps using XAML: what you need to know with Joe
Stegman
Joe's the XAML guy. Get the XAML info right from the lead of
Windows 8 XAML team

Metro-style apps using XAML: Make your app shine with Marco
Matos
This is the talk that explains how to deeply integrate your XAML
application with Windows 8.

Make great touch apps using XAML with Alnur Ismail
Learn all about touch and gestures -- obviously very important
to Windows 8 Metro applications. Don't skip this one, as the
Mouse/Touch API has changed for the better.
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Stand out with styling and animation in your XAML app with John
Papa
Here's where you'll learn about styles, animations and more

Reach all your customers' devices with one beautiful XAML user
interface with Tim Heuer
Learn how to adapt to different screen sizes, resolutions and
more

A deep dive into Visual Studio 11 Express for designing Metro
apps using XAML with Joanna Mason and Unni Ravindranathan
Want to learn about the tooling? Check this out.

Future directions for C# and Visual Basic with Anders
Hejlsberg
Not required for your own Hello World app, but there's great
info in here about async and more

More Videos to Watch
All the //build/ videos are great; there's no chaff here. Check out the full set. Here are a few others
that you'll find enjoyable:
More Windows 8 XAML
.NET and C#/Visual Basic
Windows 8 and WinRT General
Games and DirectX
C++
There are lots, LOTS more that you may want to watch. Be sure to check out the full list.