In New York, there is a march this weekend, on Sunday March 24 starting at 1 pm:

On Sunday, March 24, marriage equality
supporters will march from the historic Stonewall Inn to Washington
Square Park to express support and solidarity with those who fight for
marriage equality across the country, and especially before the Supreme
Court. At Washington Square Park, supporters will rally for freedom for
everyone—including our gay and lesbian family members, friends,
co-workers, and neighbors. The rally will feature flag dancers, singers,
and speeches.

Marriage Equality USA, GLAAD, Gay Men’s
Health Crisis, Jim Owles Liberal Democratic Club, Stonewall Democrats of
New York City, Lesbian & Gay Democratic Club of Queens, Democratic
Leadership for the 21st Century, Equality Beyond Gender, New York State
Democrats, NYC for Action, Dignity New York, Chelsea/West Village for
Change,The Bronx LGBTQ Center, Heritage Of Pride, Henrietta Hudson,The
LGBT Community Center, Manhattan Young Democrats, LAMBDA Legal, Brooklyn
Community Pride Center, Lambda Independent Democrats of Brooklyn,
Greater NYC for change, Shelter of Peace, Congregation Beit Simchat
Torah, Camp Highlight, Democracy for New York City, NYU Law Democrats,
Democracy for America, Empire State Pride Agenda, The Queens Pride
Center, The Anti-Violence Project, AM 1600 WWRL, Imperial Court of New
York, Montclair State University LGBT Center, Middle Collegiate Church,
JQY, The Global Gender and Sexuality Project at The New School and The
Stonewall Inn are together for this one.