Check out www.CommonGroundMeditation.org in Minneapolis. They offer retreats in southern MN, and recently purchased a retreat property in Menomonie, WI.
One interesting note about the vipassana retreat mentioned: ten years ago, I participated in a 10-day vipassana retreat and absolutely loved it! I recently contacted Dhamma Visuddhi in WI to register for another 10-day retreat. In the application, I answered the question about whether or not I teach meditation. (I teach a two-credit course at a local community college.)
It was a shock to me when I was informed that I could attend the retreat, but if I wished to attend any additional retreats I would have to give up teaching meditation and only practice the vipassana technique as taught by Goenka.
I would have completely understood if they had requested that I not teach any of their techniques, but to require that I stop all teaching seems wrong to me. I decided not to attend. What a shame.
If I had omitted that I teach meditation, none of this would have come to light, but it would not have been truthful.