This page is pretty much self explanatory.  Listed below are the 10 most popular songs on the website,   The top 10 is determined by how many times a song completely loaded and played.  (songs that are only partially loaded or played  do not count) 
Generally the top song is one that is picked up by a website or message board.  I think this is why songs about specific teams  tend to lead the pack.   You will also see the top 10 from past years listed below.   

2006 Top 10
Follow Dodgers
Dodgers Fan dance
Fightin Phils
TMO Memoli
JJ Dimaggio
TMO Andrews
Brooklyn BB Fan
GO GO SOX
TMO Ferko

2007 Top 10
Follow Dodgers
Fightin Phils
Say Hey
Baseball Baseball
Who's gonna win
TMO Hindermyer
Dodgers Fan dance
JJ Dimaggio
TMO Griffin

Fighting Phils
Follow the dodgers
Sey Hey
Amazing Willie Mays
TMO Hoosier
I love Mickey
Dodgers Fan Dance
Red Sox Polka
TMO Frankie Masters
BBC Recording