Big Numbers:

http://www.bbc.co.uk/skillswise/numbers/wholenumbers/whatarenumbers/writingbignumbers/bigorder.swf

http://www.wmnet.org.uk/wmnet/custom/files_uploaded/uploaded_resources/853/PlaceValueChartv4.swf

http://www.mathcats.com/explore/reallybignumbers.html

http://www.scottaaronson.com/writings/bignumbers.html

Game to think of the biggest number

http://www.bliner.com/scott/bnum.html

http://www.bbc.co.uk/skillswise/numbers/wholenumbers/whatarenumbers/writingbignumbers/game.shtml

Visualizing:

http://www.kokogiak.com/megapenny/1.asp

http://www.vendian.org/envelope/dir0/getting_a_feel.html