There are two methods for Call Sign Lookups
1. Through QRZ.com
2. If you know the person has APRS
you can track them with FINDU.com

 

QRZ callsign lookup:  
Callsign lookups provided by qrz.com

 

Locate APRS linked Hams

Enter the call sign here then click the button below

This takes you to the FINDU.COM web site