All-American Girls Professional Baseball League (1943-1954):
http://www.aagpbl.org/
A virtual scrapbook filled with articles, photographs, interviews, and statistics about the pioneering women who played professional baseball from 1943 through 1954

Ballparks of Baseball:
http://www.ballparksofbaseball.com/
History and detailed information on past, current, and future ballparks in America.

Major League Baseball Association:
http://mlb.mlb.com/NASApp/mlb/index.jsp
Official site of MLB, offering up-to-date, informative, and "exciting" baseball information.

Minor League Baseball Association:
http://www.minorleaguebaseball.com/
News, scores, and general information on minor league baseball.

Negro Baseball League:
http://www.mlb.com/NASApp/mlb/mlb/history/...(URL truncated)
History, media, and information on the Negro Baseball League.

Sports Illustrated for Kids:
http://www.sikids.com/
Games, information on football, baseball, and more.

Baseball:
http://www.baseball.com
News, fantasy league information, and forums about professional baseball in America.

Baseball Reference:
http://www.baseball-reference.com
When you need a quick list of the players with 500 home runs or 300 wins, this is the site for you.

SI Major League Baseball:
http://sportsillustrated.cnn.com/baseball/mlb/
Sports Illustrated Online's Major League Baseball section.