Three indespensible books for .NET developers

• Framework Design Guidelines: Conventions, Idioms, and Patterns for Reusable .NET Libraries (2nd Edition)
  by Krzysztof Cwalina , Brad Abrams
• CLR via C#, Third Edition
  by Jeffrey Richter
• Patterns of Enterprise Application Architecture
  by Martin Fowler

Web Development

• HTML & XHTML: The Definitive Guide, Fifth Edition
  by Chuck Musciano , Bill Kennedy
• Eric Meyer on CSS: Mastering the Language of Web Design
  by Eric A. Meyer
• Web Style Guide: Basic Design Principles for Creating Web Sites, Second Edition
  by Patrick J. Lynch , Sarah Horton

For DBAs

• The Guru's Guide to SQL Server
  By Ken Henderson
• The Data Warehouse * Toolkit
  by Ralph Kimball (any book!)

Architects and Sr. Developers

• Code Complete, Second Edition
  by Steve McConnell
• Developing International Software, Second Edition
  by Dr. International
• *
  Martin Fowler (any book!)
• * Patterns & Practices
  by Microsoft Corporation (Any book in this series!)
• Writing Secure Code, Second Edition
  by Michael Howard, David C. LeBlanc

Team Leads and Project Managers

• The Art of Project Management
  by Scott Berkun
• One Minute Manager
  by Ken Blanchard
• Fierce Conversations
  by Susan Scott
• Software Engineering with Microsoft Visual Studio Team System
  by Sam Guckenheimer, Juan J. Perez
• Software Testing with Microsoft Visual Studio 2010 Team System
  by Jeff Levinson

For Designers

• The Visual Display of Quantitative Information
  by Edward R. Tufte