If original and independent research, statistical analysis, and position papers are among the hallmarks of think tanks, then the national pastime is lousy with 'em.
James -- and certain substances and naked pull-ups -- helped bring the Boston Red Sox two recent World Series titles. In think tank terms, that's like the Center for American Progress getting national health care reform through.
James and the people he influenced also led to this Michael Lewis book, and of course, to the drafting of Nick Swisher and the Greek God of Walks.
In addition to James, other key baseball tanks might be said to include: Elias Sports Bureau, Baseball Prospectus, Daniel Okrent and the advent of Rotisserie, and the Society of Baseball Researchers*. On a less quantatative bent, up in Pasadena, there's the Baseball Reliquary.