Mad Tea Lab:

• Is an “Interactive Programming” environment
  
• Gives you fast access to javascript, html, math and graphics
• Can convert your lab session to an URL that you can bookmark or send
• Is nice for prototyping dsp and synthesis algorithms
• Can assist in exploring web technology.
• Was created using a highly underrated development methodology called “scope creeping“
• Is just a single html file with a javascript
• Is around < 200 kB in size
• Uses the canvas tag for graphics (and a fallback for ie)
• Involves heavy use of innerHTML and eval()
• Is a web application that runs locally on your machine
• Could be considered a kind of hack
• Can reverse its flow to be used as a interactive solver
• Can do gamma corrected anti-aliasing
• Can also do unit conversion!
• Can Serve as recreational fun. For nerds.
• Has intentionally undocumented features
• Might have unintentionally undocumented features

Oh, by the way,
I’d recommend browsing the examples as a kind of intruduction!