Giancoli text book link to chapter on simple harmonic motion.
http://cwx.prenhall.com/giancoli/chapter11/deluxe.html
Simulation website that shows graphs of position, velocity, petential and kenetic energy of a spring oscillator. Change the variables to see how the graphs are affected.
http://canu.ucalgary.ca/map/content/shm/springEnergy/simulate/page2.html
PhET link to masses on a vertical spring.
http://phet.colorado.edu/en/simulation/mass-spring-lab