Pond5 - Pond5 is an online marketplace for royalty-free media that offer stick footage, stock music, stock photography, effects, images, and 3D models.
isk-daemon - isk-daemon is an open source database server capable of adding content-based (visual) image...
Image Search Keyboard - Search Google Images right in your keyboard
IQDB - Multi-service image search
Bing - Bing helps you turn information into action, making it faster and easier to go from searching to doing.
TinEye - Reverse Image Search to help find an image's source, duplicates or altered versions.