Barack Obama's victory margin from November 4th now stands at 9,124,522 votes, and will probably grow a bit more once states like Illinois, New York and California finalize their counts.
This is the 6th largest victory margin of all time, and the largest ever by a non-incumbent.
Year Candidate....Incumbant?.......Margin
1972 Nixon...........Yes..........17,995,488
1964 Johnson........Yes..........17,951,287
1984 Reagan.........Yes..........16,678,120
1936 Roosevelt......Yes..........11,070,786
1956 Eisenhower....Yes...........9,551,152
2008 Obama..........No...........9,124,522*
1980 Reagan..........No...........8,423,115
1996 Clinton..........Yes...........8,201,370
1924 Coolidge........Yes...........7,377,547
1988 Bush............ No............7,077,121
* Provisional
comparison charts and more details at link:
http://www.fivethirtyeight.com/2008/11/obama-popular-vote-margin-largest-ever.html