The biggest local running club is Taconic Road Runners. They organize local races throughout the year, and have training runs on Wed and Sat mornings. Check out their website for more information :
Taconic Road Runners Club. This will be your best bet in getting involved in local running community. In terms of finding races to participate in I like
Running in the USA - Home where you can search by state, and of course there is
www.nyrrc.org- ton of races in the city! Happy miles!!!