From The PEW Researchers

If the Supreme Court legalizes gay marriage throughout the country, the United States would join more than a dozen other countries that already allow gay and lesbian couples to wed in all of their jurisdictions. The first nation to legalize gay marriage was the Netherlands in 2000. Since then, several other European countries – including Spain, France and all of Scandinavia – have enacted laws sanctioning gay marriage. Outside of Europe, same-sex marriage is now legal in Argentina, Brazil, Canada, New Zealand, South Africa and Uruguay, as well as in parts of Mexico.
                       From PEW's 5 Facts about Same-Sex Marriage. 

ABC-TV offers some quotes from the justices in today's oral arguments. A decision is expected in June, Gay Pride Month.