World Series home field advantage
As far as I know, MLB has always rotated home-field advantage in the World Series between the National and American League representatives to the Fall Classic.
From 1986-2002, after the DH had entered the American League (in 1973), MLB decided to allow the home team to have the additional advantage of playing by the DH (or not) rules of their league. (There were no DH's in the WS from 1973-1975. And from 1976-1985, there were DH's in all WS games-- only during even years.)
I always thought this was unfair-- since it gave a double advantage. To note, why not have the NL rules for AL home games and vice versa? And it seemed to make a key difference in a few series-- most notably those won by the Twins in 1987 and 1991 (since they only won home games on their way to the championship).
After a tie in the 2002 All-Star Game, MLB Commissioner Bud Selig decided to have the winning league in the All-Star Game receive home-field advantage in the World Series-- so that "the game would now matter".
This year, Tampa Bay will be the home team since the American League won the All-Star Game again. Interestingly, the AL's victory came at the expense of Philly closer Brad Lidge. Ironically, in a spectacular comeback year, Lidge had 46 saves without "blowing" an opportunity for a save. But his loss in July leads to the Rays advantage in October.