The Factor Game http://illuminations.nctm.org/ActivityDetail.aspx?ID=12
Geometric Fractions http://math.rice.edu/~lanius/Patterns/
Pythagorean Theorem http://standards.nctm.org/document/eexamples/chap6/6.5/index.htm#applet
More fractions (and Grampy) http://www.visualfractions.com/
Measuring Circumference http://www.arcytech.org/java/pi/measuring.html
Fibonacci http://www.learner.org/exhibits/renaissance/fibonacci
Similarity with Rectangles http://standards.nctm.org/document/eexamples/chap6/6.3/index.htm
Tesselations - which polygons tesselate? http://www.coolmath.com/lesson-tessellations-1.htm
SAT Practice Test http://www.4tests.com/exams/examdetail.asp?eid=6