Acording to top40.about.com a chart was compiled every year listing the top 10 songs of the summer according to chart data and here's what they got for #1 each year...
2000 - Aaliyah Try Again
2001 - Lifehouse Hanging By A Moment
2002 - Nelly Hot In Herre
2003 - Beyonce feat Jay-Z - Crazy In Love
2004 - Usher Confessions, pt. II
2005 - Mariah Carey We Belong Together
2006 - Nelly Furtado featuring Timbaland Promiscuous
2007 - Fergie Big Girls Don't Cry
To see the Top 10 of each year go here...
http://top40.about.com/od/toppopsong..._the_2000s.htm
I think this is actually pretty accurate for the most part