We went to Hudson Valley Nursery today and had such a good time! The butterfly house was small, but only $3 pp, so definitely a good deal. There were so many beautiful butterflies--I took almost 100 pictures. The place also has a free BBQ on Saturdays and Sundays, so you can just get some free food there (we didn't, because we had plans to go out to eat, but it smelled so good).
All in all, it's a decent hike for a half hour thing, so plan something else to do, but it was really cute and we had a great time. We're going to try the one in Camden another time (it's by the aquarium).