Here are just a few of the many results for an easy Google search:

http://www.google.com/search?q=infinity+is+not+a+number

http://nrich.maths.org/2756

(I particularly like this one, as the author is a top mathematician, here seen writing in her younger days.)

http://mathforum.org/library/drmath/view/62486.html

(Ask Dr. Math pages are generally good for answering elementary questions from students.)

http://scienceblogs.com/goodmath/2008/10/infinity_is_not_a_n...

(Of course the Good Math, Bad Math blog has a page on this issue.)

http://www.physicsforums.com/archive/index.php/t-65355.html

(A discussion on Physics Forum illustrating how some of the confusions about infinity arise.)

http://www.jimloy.com/algebra/two.htm

(Jim Loy's page on this is interesting too.)