The Wisconsin Geological and Natural History Survey has a well organized, appealing website.  Their data is easy to find although there is not much GIS data available.

Although because I am more interested in sample data sets than anything, the GIS data they do have–statewide geologic map; pleistocene geology, precambrian geology, quaternary geology, (surficial?) geology and bedrock geology for various counties–may actually be a great reference.  Other than the statewide geologic map, the data is available on a per-publication basis.

Some other data is available in the open-file reports.

They also have a well contructor’s reports CD available for purchase, albeit only scanned images of the wells and a very simple database.

Other .pdfs are also available of various state-wide maps and for various open-file reports.

I found some interesting things while reviewing the data I downloaded.

1. There is minimal attribution on the data–enough to symbolize it.
2. Dip & Strike triangles are captured as points with attribution of the horizontal azimuth and inclination.
3. One item I found odd at first but quickly grew to appreciate is that they provide a georeferenced .sid of  each plate.  This allows you to directly compare the digital data to the final cartographic product.  Think this may be a keeper of an idea.