"The only church that truly feeds the soul, day-in day-out, is the Church of Baseball."
Annie Savoy (Susan Sarandon) in Bull Durham (1988)
Let us play:
Baseball and religion
To the utter bewilderment of the rest of the world, the United States is at the leading edge of scientific advance, yet remains one of the most religiously devout countries in the non-Muslim world. Church attendance and professions of faith in miracles are almost without parallel in the developed world. It may not be coincidental that the great late cartoonist Charles Schulz, creator of Charlie Brown and the rest of the "Peanuts" comic strip gang, had a deep appreciation for baseball and often made clear allusions to his religious faith, though in a gentle, non-proselytizing way. 
While this wide-eyed, potentially gullible mindset may be conducive to exaltating athletic competition to the spiritual plane, we probably shouldn't carry the analogy between Our National Pastime and our nation's religious heritage(s) too far. Indeed, in our modern, liberal, secular society we are perfectly free to poke fun at the pretensions of establisment churches. By "civic religion," we simply refer to the fact that since the days of the Civil War, baseball has been the "gravitational field" that pulls us all together. It inspires just the right combination of individual excellence and group loyalty. It creates a common bond among Americans of all classes, races, regions, religions, generations, and walks of life. It builds a sense of community and national identity and makes us feel proud to be Americans. Is this a great country, or what?
Highly recommended: Opening Day Genesis by Glenn Burkmeier (hat tip to Rudi Riet)
This theme of "civic religion" is explicit throughout my favorite book about baseball stadiums, Green Cathedrals, by Philip J. Lowry (Addison Wesley, 1992). This amazing book is, on one hand, a comprehensive and extremely useful factual database about every single stadium in which a major league game has ever been played, including temporary "neutral" venues as well as stadiums used by Negro League teams. Indeed, it is the single most important source of data for most of the stadium pages on this Web site, and I am indebted to Mr. Lowry for putting in so much effort to gather all that information. On the other hand, Green Cathedrals is replete with effusive lyrical prose on all the subtle "mystical" qualities of the stadiums he covers. The author somehow manages to deal with both the technical "yin" and the artistic "yang" of baseball stadiums.
Baseball and politics
Just as there is no crying in baseball (as Tom Hanks said in A League of Their Own), there is no room for politicking. You can be a scruffy New Deal leftist like Studs Terkel or a blue-blood conservative elitist like George Will, and you will fit in just fine, as long as you park your political opinions at the door. In Ken Burns' Baseball documentary series, Bill "Spaceman" Lee, the psychedelic pitcher from the 1970s, criticized baseball owners in terms that were clearly Marxist. In the 2004 presidential campaign, in contrast, Hall of Fame catcher Johnny Bench campaigned for President Bush in the crucial state of Ohio, possibly changing the course of history. The return of baseball to Our Nation's Capital in 2005 offers hope that the sharp hostilities between the parties may gradually be eased by the resumption of the old custom of legislators and activists going out to the ballpark together. Whatever one's political affiliation, the image of the President throwing out the first pitch at RFK Stadium brings a warm, confident sense that what unites the country is stronger than what divides it.
Baseball and business
Professional sports is by nature a contradicton in terms, and could not exist in a society that lacked deep reverence for customs and ethical mores. Given the constant temptations to cheat for monetary gain, professional sports is a gigantic leap of faith. Thus, there will always be latent tensions that threaten to undermine the integrity of the sport, and nothing but fan vigilance can keep players and owners honest. In a nominally capitalist society such as ours, there is a higher value placed on individual competitive effort, whereas socialist societies place a higher value on team work. Among all sports, baseball seems uniquely oriented toward highlighting both individual and cooperative effort. But is professional baseball in the USA really an example of capitalist free enterprise, or is it a medieval cartel? The strike of 1994 is often blamed on "greed" but it is probably more the result of the antitrust exemption Major League Baseball was granted early in the 20th century. This removes the normal disciplinary market incentives that keep competitive businesses "honest." Some basic reform is needed to attract quality players while maintaining a semblance of balance between big markets and small markets, but there are no easy solutions in sight.
See MLB Franchises.
Baseball and kids
Many non-believers deride baseball fans as hopeless sentimental fools, out of touch with today's youth, and there may be some truth to that. It is important to keep in mind, however, that the love of baseball and its hallowed past is more than nostalgia, it is a lively, active literate interpretation of a saga that evokes the finest human qualities while embracing the funky, nitty-gritty realities of urban life. The scruffy street punks who venerated Babe Ruth back in the 1920s are the counterpart to the rap music fans and X-treme skateboard fanatics of today's hip-hop generation, defying authority in the finest tradition of Patrick Henry. Major League Baseball is not stupid, and their marketing departments are constantly inventing clever ways to appeal to the sensibilities of kids and adolescents. Hence the savvy use of the Goo-Goo Dolls' hard-rock rendition of Take Me Out to the Ballgame in the late 1990s, and the hip slogan, "I Live For This!".