One example of human computation in citizen science is Feederwatch, here at Cornell’s Lab of Ornithology.
Project FeederWatch is a winter-long survey of birds that visit feeders at backyards, nature centers, community areas, and other locales in North America. FeederWatchers periodically count the birds they see at their feeders from November through early April and send their counts to Project FeederWatch. FeederWatch data help scientists track broadscale movements of winter bird populations and long-term trends in bird distribution and abundance.
More at the Feederwatch website.
(Contributor: Andrew Mullen)