Playground, with everything set up in global namespaces for the developer console and a Scene setup with node debugging information below.
Renderer comparison, for inspecting rendering differences between Canvas/SVG/DOM/WebGL. Sometimes requires a reload to work properly, due to some Require.js issues.
Display fuzzer, performs random operations on a scene graph with a display in an effort to trigger assertions/failures to uncover any existing bugs.
Text bounds comparison, for evaluating different methods of computing text bounds.
Canvas Composite Test, visual inspection of composite operations
Canvas browser differences, for working around differences (bugs?) in browser Canvas 2D implementations.