Twin Cities Acoustic Music Calendar for Minneapolis/St. Paul
The comprehensive Twin Cities acoustic music calendar for Minneapolis, St. Paul, and surrounding Minnesota communities, covering bluegrass, old-time, country, Celtic, Cajun, Nordic, blues, folk, Americana, singer/songwriter, and contemporary folk music. It includes major events in the upper Midwest, including Wisconsin, Iowa, North Dakota, and South Dakota. (from the site's homepage)
You may also find user contributed jam sessions near Minneapolis/St. Paul on folkjam.org.