Face++ - API for face detection – also detects gender, age, pose
Pixaven - Modern GPU-powered image processing API
Facesoft - The world's most accurate face recognition algorithm
tiny.pictures - Real-time image-processing, optimization, and Content Delivery Network
Facial Recognition by FB - Get notified if someone tries to use your photo on Facebook
Sirv - Dynamic image processing, hosting and rich-media for retailers and eCommerce.