TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.
Pond5 - Pond5 is an online marketplace for royalty-free media that offer stick footage, stock music, stock photography, effects, images, and 3D models.
GImageReader - gImageReader is a simple Gtk/Qt front-end to the Tesseract OCR Engine.
Image Search Keyboard - Search Google Images right in your keyboard
Yandex.Images - search for images on the internet, search by image
Bing - Bing helps you turn information into action, making it faster and easier to go from searching to doing.