Matt Warren, who has been one of the lead developers on many aspects of LINQ, recently posted two very interesting stories describing The Origins of LINQ to SQL, and IQueryable's Deep Dark Secret.  In his first post on the Origins of LINQ to SQL, Matt talks about some of the previous dead projects, such as ObjectSpaces and WinFS, that influenced LINQ to SQL.  I found it interesting to hear about how LINQ to SQL came to be, and some of the internal politics that had to be overcome to make it a reality.  In his second post, IQueryable's Deep Dark Secret, Matt talks about how a call from Don Box eventually led to what is now at the core of LINQ, IQueryable.