I'm playing around with writing a Chrome extension that identifies countries of the world in the browser and marks them up with expandable, at-a-glance summary data for that country, like GDP per capita, composite index scores (HDI, MPI, etc.), literacy rate, principal exports and so on. I find myself regularly looking this up on Wikipedia anyway, and figured I'd remove the inconvenience of doing so.

This example probably isn't that useful for everyone, but it got me wondering what other sets of things could be marked up in the browser in this way. Another example that occurred to me was legislature voting records, where a similar plugin would provide easy visibility of how elected representatives voted on legislation. Again, not useful for everyone, but I could imagine political junkies getting some use out of it.

Such a set of mark-uppable entities would have to be either identifiable by format (like an ISBN) where the data could be fetched from a remote source, or a finite list of a few hundred items (like countries), where the data could be stored locally. What kinds of things would you like this sort of visibility on in the browser? Is there a set of entities you find yourself tiresomely looking up data for over and over again?

(Partly inspired by the Dictionary of Numbers)