In an email today I was asked "What books did you find most influential in your professional career?"  Honestly, I've been much, much more influenced by the people I've worked and interacted with.  For that matter, blogs and podcasts pack a lot of intellectual punch these days.  That being said, here's my list, but you'll notice that every book is at least a couple years old and none of them are .Net specific.  That might be because publishing isn't as important or it might be because I just haven't thought to buy a development book lately.

• Refactoring by Martin Fowler -- The best book I know for low level code quality
• Patterns of Enterprise Application Architecture by Martin Fowler -- Basically defines much of the vocabulary for designing enterprise systems
  
• XP Explained by Kent Beck, version 1 -- Otherwise known as the "White Book" or occasionally I'll call it "Chairman Beck's Little White Book" when I'm irritated at some example of XP zealotry.  I'm saying version 1 here in specific because (I've didn't bother reading XPE2) Beck does such a great job in laying down the principles and the "why" behind Extreme Programming.
• The Pragmatic Programmer -- I really don't need to explain this one
• Mary Poppendieck's talks and podcasts on Lean Programming.
• Object Design by Rebecca Wirfs-Brock -- She doesn't get anywhere near the recognition she deserves.  I find that Responsibility Driven Design is far more useful and effective for crafting a design than UML modeling, but the dadgumn picture doodling became a phenomenon
  
• Working Effectively with Legacy Code by Michael Feathers -- A survival guide for dealing with legacy code
• Applying UML and Patterns by Craig Larman -- Awesome introduction to OO design
• Debugging the Development Process: Practical Strategies for Staying Focused, Hitting Ship Dates, and Building Solid Teams by Steve Maquire
  

Books that are worth reading:

• Code Complete V2 by Steve McConnell
• Domain Driven Design by Eric Evans
• Give the original Gang of Four book a read sometime
• Agile Software Development, Principles, Patterns, and Practices by Robert C. Martin -- pssst, the principles are all online somewhere.  I've touched on many of them in my posts as well