CamFind - CamFind is the very first mobile application that can photograph, identify, and provide information...
Yandex.Images - search for images on the internet, search by image
IQDB - Multi-service image search
TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
SauceNAO - SauceNAO is a reverse image search engine.
NISE - The NISE Image Search Engine is a reverse image search engine (like tineye.