Since 2006 the University of Oxford’s Faculty of English and IT Services have been running a series of crowd-sourcing projects using what is known as the Oxford Community Collection Model (OCCM). The first was the Great War Archive which supplements the major digitized collection of primary source material around the poetry from 1914-1918 – ‘The First World War Poetry Archive’. The Great War Archive was then followed by Oxford at War, Europeana’s 1914-1918 project (not on Omeka but see here), Lest We Forget, and Project Woruldhord (contributed material for the study of Old English).
The OCCM is detailed at a site on ‘Running a Community Collection’ with other examples of successful implementation of the model.