Ohio

Ohio has done, and continues to do, a great job producing GIS datasets and distributing over the Internet at no cost.  Given the quality and amount of the data available, it'd be churlish to complain (and my complaint is very mild) but much of the data is not centrally located but distributed through the various divisions of the Ohio Department of Natural Resources (ODNR)... other (generally non geological) are distributed by other departments within the Ohio state government.

I have found these sites particularly useful:

• The Ohio Department of Administrative Services (DAS) is a great place to begin a search.  With a little digging, you can come up with an enormous amount of useful data.  Of particular interest is the GeoDATA ftp site, a great site for DEM's, DLG's, and DRG's.

• ODNR operates the the Geographic Information Management Systems (GIMS) which has a vast wealth of interesting data for Ohio counties and for the entire state.

• ODNR Division of Water, paradoxically, may provide more data of geologic interest then any other division of ODNR.  Of particular interest is the Statewide Aquifer Mapping Project (SAMP) which has produced an unconsolidated deposits (a.k.a. surficial geology) map of the state. I also like their collection of online maps (although their not really in GIS format)

• ODNR Division of Geological Survey produces and distributes some great GIS data and should be providing even more in the near future.

• The Ohio Department of Transportation (ODOT) has some useful GIS data.  Most of it is in .DGN format, the native format of Bentley Systems' MicroStation, a CADD software package

• The Public Utilities Commission of Ohio (PUCO... I'm not sure how they pronounce that) not only has some interesting data of it own but has links to many of the state data sources listed above