Introduction to Rocks

The Rock Cycle
http://www.k5chalkbox.com/sedimentary-rock-formation.html .  


Edible Igneous Rocks

http://www.pages.drexel.edu/~ks73/Ediblerocks.htm

Students simulate the rock cycle and end up with igneous rock fudgehttp://lessonplanspage.com/ScienceRockCycleFudge58.htm/ 

This is a great activity that reinforces the basic concepts of how sedimentary rock is formed.  It takes a bit of preparation but makes a big impact.
http://www.primary-education-oasis.com/sedimentary-rock-formation.html

Edible Geology provides students with an easy way to remember the basic characteristics of Franciscan Complex rocks, and to enable students to connect their prior knowledge of common candies with the descriptive science of geology. 

http://www.nps.gov/goga/forteachers/loader.cfm?csModule=security/getfile&PageID=159403