Leslie Carr has identified the top 10 "hard working" UK and U.S. digital repositories based on "the number of days deposit activity that they achieved in the last year according to ROAR."
The number one U.S. repository was the RIT Digital Media Library and the number one UK repository was the University of Kent.
Read more about it at "Hard Working Repositories" and "Hardworking Repositories: Comparing UK & US."