AfterShip - AfterShip is the shipment tracking API for ecommerce businesses and marketplaces.
17track - All-in-one package tracking
PostTrack.com - Universal Parcel Tracking System
Tracktrace.delivery - Track & trace delivery status of international parcels
Parcel - Blazing fast, zero configuration web application bundler
China Post Track - China Post Track is the online parcel tracker, helps to track a shipment from the People's Republic of China. Tracking shipments from China Post