Answer:
At least 107,217 same-sex couples have been legally married worldwide, although the number is probably much larger.
This is a summary of the only available statistics I have been able to find:
In Europe:
Netherlands - 10,694 as of 12/31/07;
Belgium - 2,442 as of 6/1/05;
Spain - 19,643 as of 12/31/10;
Norway - unknown;
Sweden - 174 as of 6/30/09;
Portugal - 410 as of 6/5/11; and
Iceland - at least 1 - the prime minister of the country.
In North America:
Massachusetts, USA - 7,341 as of 12/31/05;
Canada -12,438 as of 10/06
Connecticut, USA - more than 17,000 as of 10/1/09;
Iowa, USA - 2,020 as of 3/31/10;
Vermont, USA - 1,188 as of 8/31/10;
Washington, DC, USA - approx. 5,500 as of 3/9/12;
New Hampshire, USA - approx. 1,800 as of 12/31/10;
Mexico City, Mexico - 1,815 as of 12/15/11;
New York, USA - approximately 2,400 outside of NYC as of 2/1/02;
Quintana Roo (state), Mexico - at least 80 as of 2/14/12; and,
California, USA - approximately 18,000 between June 16 and November 5, 2008.
In Africa:
South Africa - 1,572 as of 12/31/09.
In South America:
Argentina - 2,697 as of July 20, 2011;
Espirito Santo (state), Brazil - at least 1 as of January 3, 2012; and,
Alagoas (state), Brazil - at least 1 as of January 6, 2012.