I was looking for links to all the State Geological Surveys and found the Association of American State Geologists (AASG) Homepage to have exactly what I needed.

I hope to build some sort of inventory of data samples available.  If I do one a day, I can be done in 10 weeks, or about 3 months.

What I will find the most useful is data distribution methods and data structures.

The USGS has a sample web application and it includes statewide data for four states–Arizona, Idaho, Oregon and Washington, so those, along with Illinois and the states that border Minnesota will be among the first I take a look at.