An interactive multi-media lesson on real numbers, by Hippocampus
http://tinyurl.com/5zrjfy

You can view all of the interactive algebra, calculus and statistics lessons by Hippocampus at
http://www.hippocampus.org/

Two interactive powerpoints for Pi Day (March 14), by Pam Burke, along with the instructions.
Are you smarter than a 5th grader?

http://www.geocities.com/pamburke74/PIDayAreYouSmarter1.ppt
http://www.geocities.com/pamburke74/PIDayAreYouSmarter2.ppt
http://www.geocities.com/pamburke74/AreYouSmarterInstructions.pdf

And here is a Pi Day Jeopardy Game along with the instructions, also by Pam Burke. Thanks for sharing, Pam!

http://www.geocities.com/pamburke74/PIDayJeopardy.ppt
http://www.geocities.com/pamburke74/JeopardyInstructions.pdf

BTW, why do you think March 14 is Pi Day in the USA? What day is Pi Day in Australia?