The National Geological Map Database's GEOLEX provides "lithologic and geochronologic unit names" including information on "the original and current description of the unit, the type locality, geologic age, geographic extent, variations in geologic name usage, and publications that have described the unit."
GIS and computational tools like ArcGIS are best learned in a comprehensive manner during a for-credit course. But if you want to go it alone, or brush up, these are some good websites.
This is a somewhat old, but still useful introduction to GIS book by David J. Buckley. He allows visitors to download the entire full-text PDF (about 5 MB).
