Processing

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Possible complement/alternative to BYOB for computational thinking strand of course.
Pros:

• Visual
• Translates well to CC/Java
• Iteration/recursion are very natural and visual in this environment
• "Real" code

Cons:

• "Real" code
• Debugging not well supported

Resources:

• Main site: http://processing.org/
  
• Javascript port: http://processingjs.org/
  
• Online sketchpad for processingjs: http://sketchpad.cc/
  
• Book (not free but lots of free examples/resources): http://www.learningprocessing.com/downloads/