Fred W.
Yelp
The Isabella Freedman Jewish Retreat Center is one of my favorite places on Earth. A beautiful spot on two small lakes, surrounded by lush wooded hills, you feel a world away, even though it's only a couple hours from NYC. They host the Elat Chayyim Center for Jewish Spirituality, which runs numerous retreats that anyone can sign up for. I've been to 1-day, and 7-day events there, and my advice is you'll want to stay as long as you have time for.
They also host an organic farm (Adamah) and an environmental leadership center (Teva), which are possibly the best (only?) ways on the East Coast for an experience in Judaism's agricultural and earth-connected roots. They also host a lot of conferences, weddings, etc. too. And they also have a fabulous book store (also available on-line), with an especially extensive music collection.
The facilities are basic, and the rooms are "rustic" (some are a bit cramped and run-down; it's closer to a camp than a luxury hotel), but the place is kosher and wild and scenic and what more could you want?