Looking for a way to get your elementary and middle-school students interested in programming at an early age? You might try introducing them to Scratch, then taking your more advanced learners over to CodeAcademy.
Scratch, developed at MIT, is a user-friendly introduction to programming that allows students to program in pre-written blocks of code called scripts that help new programmers avoid the frustration of one missing semicolon messing up a whole chunk of code. Completed projects can be uploaded to the Scratch website where they can be viewed, commented upon, and even improved upon by others.
Although it might be tough to justify devoting major chunks of class time to this with your entire class, either of both of these sites would be outstanding for use in an elementary or middle-school tech club format.