Beginner intro: https://quantumexperience.ng.bluemix.net/qx/tutorial?sectionId=beginners-guide&page=introduction
More advanced introduction: https://quantumexperience.ng.bluemix.net/qx/tutorial?sectionId=full-user-guide&page=introduction
Nice visualization of Grover's algorithm: http://twistedoakstudios.com/blog/Post2644_grovers-quantum-search-algorithm