processing

Tweak Mode for Processing. This makes the sketch interactive while it is running - in one window the code runs with output, in the other window is the code. Drag with the mouse on numerical constants and the values change up or down and the output updates automatically accordingly. Nice idea.

heuermh/leap-motion-processing. Very interesting, because I can play with my LeapMotion controller using Processing - the overhead to get something done is much lower than going for native programs. Additionally, it is cross-platform.

mrzl/LeapMotionP5. And another Processing library for Leap Motion. This one seems to be more complete, with gestures and such. Worth checking out.

Controlling Arduino with Android using Processing. This way, you can quickly build a control system and a matching console for the Android phone with simple sketches, without having to pull out the big IDE. And since the Arduino environment is also based on Processing (at least the surface of the programming environment), it should be easy for both Processing and Arduino fans to understand the other side.