I think Appendix A is the most important appendix. It provides a list of lessons ordered alphabetically, rather than the app-by-app organization in the Table of Contents. Here is the list:
2D Transforms
Chapter 13, "Metronome"
3D Transforms
Chapter 17, "Pick a Card Magic Trick"
Chapter 45, "Coin Toss"
Chapter 19, "Animation Lab"
Accelerometer Basics
Chapter 44, "Boxing Glove"
Accelerometer Calibration
Chapter 47, "Moo Can"
Accelerometer Data Smoothing
Accelerometer, 2D Motion
Chapter 49, "Balance Test"
AccelerometerHelper
Chapter 48, "Level"
Chapter 50, "Pedometer"
Activated Event
Chapter 10, "Tip Calculator"
Alignment
Chapter 4, "Stopwatch"
Angle, Based on Accelerometer
Animation Basics
Chapter 12, "Silly Eye"
Animations, Creating in C#
Chapter 16, "Lottery Numbers Picker"
Animations, Sharing
Application Bar
Chapter 2, "Flashlight"
Application Lifecycle
Application Manifest
Chapter 1, "Tally"
Application State
ApplicationIdleDetectionMode
Chapter 9, "Fake Call"
Audio Files, Saving
Chapter 36, "Sound Recorder"
Binary Resources
Chapter 6, "Baby Sign Language"
Background Worker
Chapter 11, "XAML Editor"
Chapter 24, "Baby Name Eliminator"
Chapter 25, "Book Reader"
Bitmap Caching
Brushes
Build Actions, Content Versus Resource
Button
Cache Mode (Cached Composition)
Canvas
Chapter 5, "Ruler"
Capabilities
Charts
Chapter 29, "Weight Tracker"
Check Box
Clipping
Closing Event
Color Animations
Chapter 15, "Mood Ring"
Color Picker
Combo Box
Composition Target's Rendering Event
Chapter 30, "Cowbell"
Content Controls
Content Presenter
Context Menu
Chapter 26, "TODO List"
Control Templates
Coordinates
Chapter 8, "Vibration Composer"
Copy & Paste
Currency Formatting
Custom Controls
Custom Fonts
Chapter 20, "Alarm Clock"
Data Binding
Chapter 23, "Baby Milestones"
Data Contract Attributes
Data, Shipping with Your App
Data Templates
DataContractJsonSerializer
Chapter 39, "Paint"
DataContractSerializer
Date Picker
Chapter 7, "Date Diff"
DateTimeOffset
Chapter 21, "Passwords & Secrets"
Deactivated Event
Decryption
Deep Zoom
Chapter 41, "Deep Zoom Viewer"
Dependency Properties
Chapter 18, "Cocktails"
Deserialization
Disabling Automatic Screen Lock
DoubleAnimation
Double-Tap Gesture
Drag Gesture
Chapter 42, "Jigsaw Puzzle"
Drop Shadows
Dynamic XAML
Easing Functions
Ellipse
Email Launcher
Embedded Resources
Emulator-Specific Code
Chapter 3, "In Case of Emergency"
Encryption
Event Bubbling
Event Triggers
Filmstrip-Style Swiping
Chapter 28, "Alphabet Flashcards"
FindElementsInHostCoordinates
Chapter 40, "Darts"
Flick Gesture
Fonts, Custom
Frame Rate Counter
FrameReported Event
Chapter 37, "Reflex Test"
Gesture Listener
Chapter 43, "Spin the Bottle!"
Gradient Brushes
Graphs
Grid
Hardware Back, Start, & Search Buttons
Hit Testing
Icons
Image
Image Brush
Image Cropping
Indeterminate Progress Bars
Ink Presenter
INotifyPropertyChanged
Input Scopes
Inertia, Simulating
Isolated Storage
JSON Serialization
Keyboard, On-Screen & Hardware
Keyframe Animations
Chapter 14, "Love Meter"
Launching Event
Line
Line Breaks
Line Height
List Box
List Box Item
List Box Items, Stretching
List Box, Multi-Selection
List Picker
Local Databases
Lock Screen (Disabling or Running During)
LongListSelector
Looping Selector
Looping Sound
Chapter 31, "Trombone"
Manipulation Events
Margins
MediaElement
Chapter 33, "Subservient Cat"
Message Box
Microphone Audio Playback
Chapter 35, "Talking Parrot"
MultiScaleImage
Multithreading
Multi-Touch
Chapter 38, "Musical Robot"
NetworkInterface.InterfaceType
Chapter 32, "Local FM Radio"
Object Animations
Obscured Event
Observable Collections
One-Time Actions
Opacity Masks
Orientation Basics
Orientation Lock
Padding
Page Navigation
Page State
Pagination
Panorama
Chapter 27, "Groceries"
Password Box
Path
PerformanceProgressBar
Perspective Transforms
Phone Launcher
Phone Theme Resources
Photo Chooser
Picker Box
Pie Charts
Pinch Gesture
Pivot
Point Animations
Polygon
Polyline
Popup
Progress Bar
Progress Bar, Indeterminate
Property Paths
Quick Jump Grid
Radio Button
Radio Tuner
Reading & Writing Files
Chapter 22, "Notepad"
Reading & Writing Pictures
Rectangle
Repeat Button
Resources
Rotate Gesture
RotateTransform
Routed Events
Runs
ScaleTransform
Screenshots, Taking from Phone
Scroll Viewer
Seadragon
Serialization
Settings
Settings Pages
Settings Page Guidelines
Shaking Detection
Chapter 46, "Noise Maker"
Silverlight for Windows Phone Toolkit
Silverlight Toolkit
Size Properties
Slider
Sound Detection
Chapter 34, "Bubble Blower"
Sound Effects
Sound Looping
Sound Manipulation
Sound, Playing Backwards
SoundEffectInstance
Splash Screen
Stack Panel
Status Bar
Storyboard Basics
Storyboards as Timers
Storyboards, Checking Status
Stretch Gesture
Styles
Tag
Text Box
Theme Detection
Throwing Detection
Tilt Effect
Time Picker
Timers
Toggle Button
Toggle Switch
Tombstoning
Touch Points
Tracking Individual Fingers
Triggers
Turning-Over Detection
Two-Way Data Binding
Undo & Redo
Unobscured Event
URL Encoding & Decoding
User Controls
UserIdleDetectionMode
Value Converters
Vector Graphics
Vibration
Video
Visibility
Visual State Manager (VSM)
Walking Motion
Web Browser Control
Wrap Panel
WriteableBitmap
XAML Reader
XAML Resources
XAML-Defined Elements, Naming
XML Namespaces
XmlSerializer
XNA
Z-Index
Zoom Gesture