These following resources provide great info on everything from properly fitting bikes to chain cleaning with tooth brushes to what to look for when buying your first bike.
Beginners Guide to Mountain Biking by Sacred Rides
Fat Bike Best Practices-A Guide to sharing the trails with skiers, snowshoers and moose
101 Tips for First-Time Cycle Tourists by TDA Global Cycling
Illustrated Bicycle Maintenance Guide for Road and Mountain Bikes by Bicycling