Martin Fowler, ThoughtWorks
Martin Fowler is an author, speaker, consultant and general loud-mouth on software development.
He concentrates on designing enterprise software - looking at what makes a good design and what practices are needed to come up with good design. He has pioneered object-oriented technology, refactoring, patterns, agile methodologies, domain modeling, the Unified Modeling Language (UML), and Extreme Programming.
He's the Chief Scientist at ThoughtWorks - an international application development company, and has written five books on software development: Analysis Patterns, UML Distilled (now in its 3rd edition), Refactoring, Planning Extreme Programming (with Kent Beck), and Patterns of Enterprise Application Architecture. I also write articles regularly on my site at Martin Fowler.