Smarty - Smarty provides address validation, autocomplete, geocoding and reverse geocoding services covering addresses in over 240+ countries.
Loqate - The Standard in Global Address Verification
AddressZen - Effortless Address Lookup.
Addressy - Addressy is address verification software that captures and verifies addresses on websites.
Lob - A simple API to integrate print & mail solutions into your applications.
Addressify - Addressify is an API that allows developers to implement address verification, validation and autocomplete for Australia in their apps.