There are many. Union de Jovenes Dominicanos, Dominicanos 2000 (D200), Centrol Comunal Gregorion Luperon, El Club 27 de Febrero, y el Comite del Dominicano en el Exterion, just to mention a few. I participate in D2000. Check its web page: www.dominicanos2000.org
Also, this coming week is Dominican Week in NYC and there are a couple of activities taking place. So, write me e-mail if you want more info about it since I don't have the information readily available.
Best regards,
Evelyn Vasquez