WordPress Theme Search - What WordPress Theme Is That?
CloudSight - Image recognition API; send an HTTP request with an image, get a description of contents.
Blocksy - A lightningfast, innovative and supercharged WordPress theme
YOLO - Real-time object detection
LyrWP - WordPress themes / plugins / services curated.
Dashmote - Dashmote bundles stock image providers to make finding stock images as easy as possible.