Lagerstatten are locations containing high fossil incidence rates.
There are two types of Lagerstatten--conservation and concentration. Conservation Lagerstatten are locations where a high incidence of exceptionally preserved specimens have been found including. Concentration Lagerstatten are sites that, as the name implies, have extremely high numbers of specimens.
A great stratigraphically ordered catalogue of famous Lagerstatten from around the world with descriptions of location, geologic setting, fauna and flora, taphonomy and additional links and references is located at: http://palaeo.gly.bris.ac.uk/palaeofiles/lagerstatten/stratlist.html