Ken Burns' excellent (and incredibly thorough) documentary on Baseball from 1840's to 2009 is now on YouTube to view in its entirety (unless the copyright lawyers get it taken down)

And absolute must watch for all baseball fans.   

1st Inning:1840 -1900

2nd Inning: 1900-1910

3rd Inning: 1910-1920

4th Inning: 1920-1930

5th Inning: 1930-1940

6th Inning: 1940-1950

7th Inning: 1950-1960

8th Inning: 1960-1970

9th Inning: 1970-1993

10th Inning: 1994-1998

10th Inning: 1999-2009