It quacks like a duck, but it’s tinkertoys on the inside
So Steven Frank (of Panic, purveyors of fine Mac software) has this crazy gleam in his eye, thinking about the possibilities of SDL and Lua (a lightweight scripting language) to create easily-tweakable cross-platform applications. Specifically, after attempting to live with “modern” PDAs, he’s obsessed with the possibility of creating a Newton-analog environment to run on modern hardware. He’s whipped up a tiny mockup for OS X.
It’s kinda nifty. Doesn’t do that much, but you can pop open the package and easily tweak the small scripts that describe all the behavior. I think that things like this and PyObjC are creating an interesting middle ground of first-class GUI applications that are easy for end-users to hack without installing crazy heavyweight environments or development tools. Konfabulator is also interesting in a similar way (easy to hack), though its apps aren’t first-class, and the user has to buy and install the platform, which is an annoying barrier to entry.