Teaching modern C++, as opposed to warmed up C in Modern C++.
Scripting user interfaces with images in Sikuli. Interesting, if inherently brittle.
Isometric in browser game development in JS and HTML5 canvas,
Pyparsing - some or all of the power of Parsec without the brain hurt of Haskell. MARS : a MIPS assembly IDE and simulator in Java, also usable as a cmdline emulator for a compiler tester.
The half float type - 16bit floating point, somewhat uncommon to find, but present in OpenCL. Conversion routines between float and half here, and here and here.