In the news:
National Geographic - The Drying of the West
Drought in the West Linked to Warmer Temperatures
Climate Sciences Revealed - Tracking the Warming Planet
Southwest headed for permanent drought

For more paleoclimate perspective:
http://www.ngdc.noaa.gov/paleo/drought/drght_home.html

For current and recent drought conditions:
https://www.ncdc.noaa.gov/

NOAAs Drought Information Center:
https://www.cpc.ncep.noaa.gov/products/Drought/

Drought for Kids:
http://www.drought.unl.edu/DroughtforKids.aspx

If you would like to investigate the tree ring reconstructed drought data yourself:
The North American Drought Atlas 2004

The drought index based on weather station data since 1860 can be found at:
Palmer Drought Severity Index