Some centers of corpus rearch in the States:
Penn U.: the home of the LDC
Vassar College: Nancy Ide, designer of the ANC
Northern Arizona University: D. Biber, R. Reppen
University of California Sanata Barbara (UCSB): the Santa Barbara Corpus of Spoken american English
University of Massachusetts-Boston/University of California, Los Angeles (UCLA): ICE-US
U. Michigan: MICASE
...