Required Links:

Master Drawing Tour at the National Gallery of Art:

Private Treasures: Four Centuries of European Master Drawings http://www.nga.gov/exhibitions/2007/private/index.shtm

Strokes of Genius: Rembrandt's Prints and Drawings
Choose “Highlights” link, at the very least
http://www.nga.gov/exhibitions/2006/genius/biblical.shtm#

A Century of Drawing, Works on Paper from Degas to LeWitt http://www.nga.gov/exhibitions/2001/centdraw/intro.htm

Additional Links:

http://www.metmuseum.org/special/Leonardo_Master_Draftsman/draftsman_splash.htm

http://www.mcescher.com/Gallery/gallery.htm

http://www.getty.edu/art/exhibitions/light_water/

http://www.modernedition.com/art-articles/contemporary-drawing/contemporary-drawing.html