general information: site with lots of links for teachers and students
http://www.win.tue.nl/cs/fm/engels/discovery/

excerpt from above site:
http://www.win.tue.nl/cs/fm/engels/discovery/#age

about Henry the Navigator:
http://www.thornr.demon.co.uk/kchrist/phenry.html

about the sea route to India:
http://www.acs.ucalgary.ca/HIST/tutor/eurvoya/vasco.html

Portuguese History
http://lcweb.loc.gov/rr/hispanic/portam/first.html

Columbus:
http://www1.minn.net/~keithp/

North America:
http://www.heritage.nf.ca/exploration/default.html

American situation (Think Quest):
http://hyperion.advanced.org/11590/main.html