Scratch is a great introduction to programming for students of all ages. With its simple to understand interface, and great price point (it’s free), it is a great educational tool for every computer classroom.
Start by downloading the free application from MIT’s scratch website: http://scratch.mit.edu/
Next, take some time becoming familiar with the basic components of the application. MIT has several tutorial videos that can get you started: http://info.scratch.mit.edu/Video_Tutorials
Finally, since scratch has become so popular, there are endless resources and tutorials on the web for nearly any question you may have. A great resource is LearnScratch.org. Although this site has recently gotten a little bit slow, it provides you with a great series of tutorials and projects from beginner to advanced.
Check out some of the projects 8th grade students were able to come up with after only 5 days of instruction and work.