Listmania!
Learn .NET and C#
By an Amazon.com customer
Programming C#Programming C# by Jesse Liberty
Buy new: $29.67 / Used from: $13.00
Learn the basics of the C# programming language.
MCTS Self-Paced Training Kit (Exam 70-536): Microsoft  .NET Framework 2.0 Application Development FoundationMCTS Self-Paced Training Kit (Exam 70-536): Microsoft .NET Framework 2.0 Application Development Foundation by Tony Northrup
Buy used from: $21.23
This book will expose you to the practical side of .NET -- the "whats" and "hows". "CLR via C#" provides the "whys".
CLR via C#, Second Edition (Pro Developer)CLR via C#, Second Edition (Pro Developer) by Jeffrey Richter
Buy new: $37.79 / Used from: $17.37
Arguably the most important .NET book for a developer to read and understand. It provides a detailed explanation of how the CLR works. You'll never move past the intermediate level until you understand the content in this book.
C# in DepthC# in Depth by Jon Skeet
Buy new: $29.69 / Used from: $28.63
I've read many books about the C# language, but this one is on a different level. It covers the new features of C# 2 and 3. This is an advanced book, so you'll need to have a working knowledge of C# before you read it. In terms of depth, clarity, and concision, it's on par with "CLR via C#".
Programming .NET Components, 2nd EditionProgramming .NET Components, 2nd Edition by Juval Lowy
Buy new: $30.49 / Used from: $20.28
Great companion to "CLR via C#". Excellent coverage of .NET security.
Programming Microsoft® Windows® Forms (Pro Developer)Programming Microsoft® Windows® Forms (Pro Developer) by Charles Petzold
Buy used from: $9.69
Learn how to use Windows forms for GUI applications.
Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET LibrariesFramework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries by Krzysztof Cwalina
Buy used from: $17.75
.NET design conventions. A somewhat tedious read, but well worth it.
DebuggingDebugging by David J Agans
Buy new: $15.34 / Used from: $9.99
An excellent general purpose book on debugging. This should probably be the first debugging book you read.
Debugging Microsoft  .NET 2.0 ApplicationsDebugging Microsoft .NET 2.0 Applications by John Robbins
Buy new: $31.49 / Used from: $22.93
This is an advanced book, but you should strive to learn the material in it. As a professional developer, you will spend a lot of time debugging.
Windows Presentation Foundation Unleashed (WPF)Windows Presentation Foundation Unleashed (WPF) by Adam Nathan
Buy new: $34.64 / Used from: $28.49
A great introduction to developing .NET 3.0 GUI applications using Windows Presentation Foundation.
Programming WPFProgramming WPF by Chris Sells
Buy new: $31.49 / Used from: $25.20
The second edition of this book is probably the single best volume on WPF. Larger than Adam Nathan's book and far more practical, as well. If you're only going to get one WPF book, this is it.
Improving .NET Application Performance and Scalability (Patterns & Practices)Improving .NET Application Performance and Scalability (Patterns & Practices) by Microsoft Corporation
Buy used from: $36.46
You can get the ebook for free from Microsoft's Patterns and Practices website. This is a huge book, and I wouldn't have put it on this list if Amazon's listmania page would let me add "Maximizing .NET Performance" by Nick Wienholt. That's actually the book I recommend, but if you can't find it, this one will suffice. Performance IS important, even in managed code.
LINQ in ActionLINQ in Action by Fabrice Marguerie
Buy new: $29.69 / Used from: $19.52
Good introduction to LINQ and C# 3.0.