Installations 30000 plus
From MoodleDocs
Universidade de Brasília, http://aprender.unb.br, 34,587 users (12/20/2007)
San Francisco State University (SFSU), http://www.sfsu.edu, 89,543 users (02/07/2008) Among these 89K users, about 35,430 users are considered as currently active.
The UK's Open University, based in Milton Keynes, Buckinghamshire, England is well on the way to create the world's largest Moodle installation in a £5 Million project. It is expected to host nearly 200,000 students. OU's News item