I would also be interested in seeing a ranking in terms of articles read by the user.

While h-index and karma are great to measure, well, measurable contribution to the community, it fails to capture the contribution to the community that consists in (and this is true of a lot of other if not of all "karma policies" too):

  - sharing what one sees in this community, and spreading it through
    other channels
  - or even just using the knowledge gathered here
  - or, in the best case, using the inspiration found in this community 
    to help build a better world

I for one read HN articles and comments about 2 hours a day every single day even now at 5am on a Sunday morning after a party. This made me a better programmer, dreamer, and probably a slightly better person too.

Yet I speak little and have only a little under 300 karma. I believe, though, that I contribute somehow more to the community than what my karma shows (e.g. by spreading the word about a cool and useful technology at work - say functional reactive programming for instance - and seeing it being adopted or experimented with).

I think attendance matters, too :)

EDIT: list formatting

EDIT2: added bit about FRP cuz, you know, redux