Since an overwhelming majority of poll respondents indicated that they "get paid to do geeky things" I figure I it is safe to post on some more technical subjects, such as the book which I recently finished reading at work. (I've been struggling to find chunks of time to read this book, having started it over a year ago, so I'm glad to finally have finished it.)
Framework Design Guidelines, by Krzysztof Cwalina and Brad Abrams, encompasses a lot of the hard lessons that were learnt in bringing the .NET Framework to us. Building an intuitive and powerful programming API is a non-trivial activity, and a lot of people underestimate the importance of framework design and design testing.
This book explains a lot of concepts that are relevant to .NET developers (even if you're not explicitly building a framework) and boils each area down to a set of easy-to-understand "Do" and "Do not" rules (a lot of which are captured by the automatic analysis of FxCop and its successors).
If you want to learn from the mistakes at Microsoft, understand design principles, and build robust, easy-to-use APIs with .NET, then I'd recommend you read this book.