Books:

The Maya - Palaces and Pyramids of the Rainforest
Henri Stierlin Köln: Taschen 2004
A photographic, coffee-table book with an emphasis on Mayan architecture & art.

Cancun & The Yucatan
Nick Rider New York: Dorling Kindersley 2004
A handy pocket-sized travel guide for people travelling to the Yucatan peninsula.

The Maya
Michael D. Coe New York: Thames & Hudson 2005
This is a more scholastic style book. It's a slow read, but has tons of information.

Popol Vuh
Dennix Tedlock New York: Touchstone 1996
The Mayan book of creation, one of the civilization's few remaining texts.

Websites:

This site by Barbara McKenzie has some really detailed maps & photos of tons of Mayan sites.
http://mayaruins.com/

Muyil:
http://muyil.smv.org/
http://www.travelwithmea.com/itin_soMex_yuca8.htm
http://www.visitcancun.com/mayan_ruins_Muyil2.htm

PBS special on the Maya:
http://www.pbs.org/wgbh/nova/mayacode/program.html

Evidence of Mayan environmental degradation & deforestation:
http://news.nationalgeographic.com/news/2003/03/0313_030313_mayadrought_2.html
http://www.sciencemag.org/cgi/content/abstract/292/5520/1367
http://science.nasa.gov/headlines/y2004/15nov_maya.htm
http://news.nationalgeographic.com/news/2007/11/071115-maya-sacrifice.html

Jared Diamond, author of "Guns, Germs, and Steel" on "Why Societies Collapse":http://www.ted.com/index.php/talks/jared_diamond_on_why_societies_collapse.html

Sacbes Paper:
http://www.fiu.edu/~mizrachs/white-roads.html

On the use of "Maya" vs. "Mayan":
http://www.pauahtun.org/Calendar/maya_vs_mayan.html

Underground ruins discovered believed to be the Mayan portal to the underworld:
http://news.nationalgeographic.com/news/2008/08/080822-maya-maze.html

On the End of the Mayan Calendar in 2012:
http://www.13moon.com/prophecy%20page.htm
http://www.calleman.com/content/articles/the_tortuguero _monument.htm
http://alignment2012.com/bolon-yokte.html http://pakalahau.wordpress.com/2007/12/08/mayan-leader-announces-2012-disasters/
http://pakalahau.wordpress.com/2007/11/23/2012-prophecy-notes-on-tortuguero-monument-6/

Mayan City Discovered With Lazers - National Geographic:
http://news.nationalgeographic.com/news/2010/05/photogalleries/100520-ancient-maya-city-belize-science-pictures/

Have another good Mayan link?  Add it to the comments!