Jefferson County Open Space -great site for trail running and mountain biking. 
San Isabel National Forest Campgrounds
Colorado State Parks
USDA Forest Service, Colorado
Leave No Trace -BLM page
Colorado Search and Rescue Card -purchase a card that helps offset SAR fees.
Colorado Fourteeners Initiative -information on CFI projects and how you can get involved.
Colorado Accident Site -climbing is dangerous.

Guides & Maps

Jefferson County Open Space Maps -maps of the Open Space trails in Jefferson County. 
14ers.com -great site for doing research on Colorado 14,000ft plus peaks
SummitPost.org -great research site on peaks, routes, summit logs, current conditions.
FourteenerWorld.com -Colorado fourteeners news site.
Stacy's 14er Topo Maps -Colorado Topo maps.

Finding a Climbing Partner

SummitPost: Plans & Partners -great place to find someone with similar interests/projects.
Colorado Mountain Club Home Page -an organization to not only find people to climb with, but also help out thetrail system and promote safe and environmental climbing practices.

Books

"Colorado Fouteeners", Gary Roach
"Colorado Thirteeners", Gary Roach and Jennifer Roach
"Mountain Biking Colorado's Front Range" by Derek Ryter adn Jarral Ryter
Trails Illustrated -get the lastest trail map updated by National Geographic
"Atlas & Gazetteer: Colorado", by "DeLorme

Free Wall Paper (however any manipulation of the images violates copyright laws)

Use this image to create a link to my site
 

Animals

Colorado Herpetological Society -when you are wondering what type of reptile you ran into on the trail.