SWINY is a group for science writers. They hold regular events about various aspects of science and science communications. The SWINY listserv and job board is also a good resource if you are looking for science writing positions.
The Scientific American headquarters are in New York. If you’re interested in publishing or science writing, check out their careers page. Also, if you want to get into freelance writing, their submission page has very detailed instructions on how to propose a story.