Web resources associated with textbook:
             http://wps.prenhall.com/esm_tarbuck_earth_7

Note-the book website has links to many useful sites as well....
 

Interesting links by topic:
 

Mars exploration:
Mars rovers program (with new pictures)
Mars exploration program

Minerals:
Mineralogical Society of America
Webmineral (good database of all mineral species with pictures)
Mindat (good database of all mineral species with pictures)

Gemstones and diamonds:
Gemological Institute of America
Thaigem.com Gemstone discovery
Blue Nile Diamonds
American Museum of Natural History Virtual Diamond Exhibit
Gemological Institute of America's How to Buy a Diamond Course
Minerals.net (not comprehensive for minerals, but nice section on gemstones)

Volcanoes:
Weekly Volcano Alert (USGS/Smithsonia Institution)
Current updates on U.S. Volcanoes
USGS Volcano site

Gold:
World Gold Council
The Gold Institute
California Gold Rush Exhibit at Oakland Museum

Forensic Geology:
Raymond Murray's site (the king of modern forensic geology)
J.D. Rogers Forensic Geology page at U. Missouri-Rolla

Earthquakes:
USGS Earthquake site
Nuclear Explosion monitoring
UF seismic station data (updated every 10 minutes)

Earth's magnetic field:
NOAA geomagnetism page (includes declination calculator)

Geology of National Parks:
National Park Service site about geology in the parks

Astronomy:
Hubble Space Telescope site
The Nine Planets Site
Solar Views Image Server
Deep Sky Atlas

Meteorites and Impacts:
New England Meteoritics Site
Meteorites and Their Properties
Interactive Map of Terrestrial Impact Craters
Terrestrial Impact Craters Images

Historical Geology/History of Life/Dinosaurs:
UC-Berkeley Museum of Paleontology History of Life site (includes tectonic and geologic events)
UCMP's Dinosaur Links
 

Relative Age Dating Exercises:
Rich Harwood at Black Hawk Community College

Weather
Weather Channel
NOAA
Accuweather
Weather Underground