As it happens, Lightroom 2.0 has just the thing I daydreamed about a handful of months ago. The new version’s data includes a table of keyword co-occurrences that makes it possible to produce things like this:
This graph shows keyword relationships that occur within a hop from my “flickr” keyword — which I use to keep track of photos that I upload there. In other words, it’s sort of a descriptive keyword neighborhood of what I’ve put up on flickr.
Color is a little subjective. The darker blue, the higher the ratio between unique neighbors and total neighbors. That is, darker blue nodes are connected to relatively few unique other neighbors than the lighter blue nodes.
Of course, you could use any focal keyword for this kind of thing: Starting with a lens-specific keyword would produce a rough map of the neighborhood associated with that lens, and might reveal how I tend to use that lens. The possibilities are pretty endless — and totally a fun kick in the pants to tinker with.