Great system. I do something similar by creating a "_misc" folder out of source control. The "_" is so that alphabetically it is listed at the top and not intermixed with actual project folders.
I use it to store code snippets, prototyping scripts, misc notes that don't fit in my main folder system for notes/todos, query output, and other random items. If the _misc/ directory becomes too cluttered , then I throw most of the items into an "archive_$DATE" sub-directory (inside _misc).
I'm still working on a broader, general organization system for notes, documents, links, todos, etc... (lots of good ideas in this thread). But this works well for more ephemeral project-specific stuff.