Accord.NET Framework - Machine learning, computer vision and statistics framework for .NET
BoofCV - BoofCV is an open source library written from scratch for real-time computer vision.
OpenCV - OpenCV is the world's biggest computer vision library
FastCV Computer Vision - FastCV will enable you to add new user experiences into your camera-based apps like:
Simple Photo Gallery - Simple Photo Gallery shows up your photos in an impressive and memorable way.
SimpleCV - SimpleCV is an open source framework for building computer vision applications.