and other random guidance I've found by perusing the "on-topic / off-topic" sections of help pages,
there seems to be a need to help disambiguate sites. While the current sites page is pretty, it doesn't really do a good job of directing would-be users to the appropriate sites for their questions. Likewise, this Map of all Stack Exchange sites (except the three biggest) is interesting, but not really the answer either.
Somewhere, there should be some sort of listing that summarizes the on-topic locus of each site, and it could be as simple as a list of the sites, along with their short descriptions next to them.
Ideally, there would even be a simple little search function that would allow a user to search through all of the site descriptions as well.
Simply put, guidance around the appropriate site seems in order, and it would be nice to capture it in a straightforward fashion.