HamData http://hamdata.com/
ARRL FCC License Data Search http://www.arrl.org/advanced-call-sign-search
FCC ULS http://wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp
WM7D http://www.wm7d.net/fcc_uls/
QRZ https://www.qrz.com/
University of Arkansas http://callsign.ualr.edu/callsign.shtml
RadioQTH http://www.radioqth.net/
AE7Q Query Tools http://www.ae7q.com/query/