In my occasional noodlings on this topic, I've wondered what the dependency graph looks like. Which modules are most frequently used in other modules? (Including the recursion -- if A uses B and B uses C, D, and E, then the existence of A should increment the dependency count of C, D, and E, too.) Presumably, core modules would have the most links, but there are likely a second strata of heavily used utility modules, and so on out to narrow, single-purpose modules for particular applications. (Though those could also be very popular and worth of inclusion in a top 100 list.)