Voice message for the foundation board and administrators can be left at +1-617-206-3947.
The Foundation rarely sends out checks, and never without prior discussion with the recipient. Those checks are usually for travel or other reimbursements for GNOME contributors. If you have received a check in the mail from the GNOME Foundation that you were not already expecting, it is likely fraudulent.
GNOME Foundation
PO Box 101
Groton, MA 01450
USA