I like this site; shows a bunch of the polls in comparison.
http://www.pollingreport.com/wh2004.htmBUSH vs. KERRY: Among likely voters; with leaners, where available. (See registered voters.) 
Survey BUSH KERRY  Margin Includes Running- End Date % %  Bush Kerry  mates?    
 Zogby 8/14 Bush 43  Kerry 50   
 Gallup 8/11 Bush 50  Kerry 47  
 ICR 8/8       Bush 48   Kerry 48     
Time 8/5      Bush 44    Kerry 51     
Democracy Corps (D) 8/5 Bush 45  Kerry 52      
FOX/Opinion Dynamics 8/4 Bush 43  Kerry 48   
ABC/Washington Post 8/1  Bush 48  Kerry 49     
CNN/USA Today/Gallup 8/1  Bush 51  Kerry 47   
The only one that counts is in November though.