Recommended Retreats

Spiritsite has a solid listing of spiritual retreats all over the country.

Spirit Rock
Spirit Rock Meditation Center, Marin County, 45 minutes north of San Francisco, is dedicated to the teachings of the Buddha as presented in the Theravadan vipassana tradition. The practice of mindful awareness, called Insight or Vipassana Meditation, is at the heart of all the activities at Spirit Rock. The Center hosts a full program for beginners and those more experienced of ongoing classes, daylong, and residential retreats.

This retreat center often hosts guest lectures such as Frances Vaughn, Jack Cornfield, and many others.

Rating: Spirit Rock is a highly recommended mindfulness retreat center.

Shambhala Mountain Center

Shambhala Mountain Center is a mountain valley retreat located on 600 acres in northern Colorado. Since 1971 the Center has offered hundreds of programs on Buddhist meditation, yoga and other contemplative disciplines. Tamed by thirty years of use as a contemplative retreat, Shambhala Mountain Center is a place where one of the basic truths of Buddhism—that people can be profoundly open to the wisdom of the present moment—is always readily available.
~ From the website

Here what these sources have to say:
Yoga Journal Denver Post NPR's - all things considered NY Times