Halfbaked Software Idea (HSI) #1: CodeWiki
Integrate a desktop wiki with a source code editor/IDE like Source Insight (which uses an approach visually and workflow-wise that I think would work well with the metaphor, but not required to be Source Insight per se). Kind of Smalltalk like (well, Squeak-like anyway), with code snippets in different wiki pages, but subtly different. Write documentation and code in one wiki, and have build features in the wiki to publish both app and docs. Promotes an organic organization of code along ideas easily funneled into the wiki, as well as easy refactoring. "In theory" wikidPad could be a testbed for this, since it's wirtten in Python and includes scriptability. Literate Haskell's (and literate programming's) concept of using notation to denote the code, rather than using notation to denote comments, also seems like a good match; you could make it a part of the wiki syntax.
For that matter, it wouldn't have to be desktop only, you could build a "normal" wiki on the Web that did this also; Darius's ikiwiki, a wiki and webserver in C, makes it's own code editable. Expanding the idea so that you could write code to make other web or server-side apps seems natural, and this would also allow a kind of distributed collective programming and refactoring.
Clearly there are safety and security concerns, but it seems compelling. One interesting option would be to see this done in E, but that shouldn't stop people from playing with this concept generally.
