Colorado Geological Survey
Good source for information about geological hazards and problematic soil conditions in Colorado.

US Geological Survey Earthquake Hazards Program
Map-based site to find out about recent earthquakes in the US and the world.

US Geological Survey National Seismic Hazard Maps
Map-based site the shows the probabilistically determined peak ground accelerations for the US.

Terraserver
Source for air photos and topographic maps for anywhere in the US.

Geographic/UTM Coordinate Converter
Useful utility site to help you convert UTM coords to Lat Long and the other way around too.

Colorado Association of Geotechnical Engineers
An organization for professional engineers. CAGE is committed to the advancement of the practice of geotechnical engineering for the benefit of public safety and the geotechnical engineering profession in the State of Colorado.

Association of Engineering and Environmental Geologists
AEG offers information on environmental and engineering geology useful to practitioners, scientists, students, and the public. The AEG website offers interesting information about geologic hazards and engineering geology issues.