I dont know any in New York, but in Philidelphia, Tennessee is the best camp ever. Its called Shadow Mountain farm, and its a all girls camp. They have one week, one and half week, and two weeks sessions, depending on your experiance. Its English riding though, so give us some more info on what you do. Its tons of fun and they are all very welcoming and you will have great friends at the end of camp. I love going =) Their website is:
smfhorsecamp.com
But i know that in some of my horse magazines they have camps advertised and im sure ive seen some in New York. Just check that out maybe. You can also google it.