I came across a nice article on a Silverlight 4 application that does real-time face detection (without having to spend a dime on commercial licenses to any APIs) on the Coding4Fun site which features unusual but interesting applications built on the .NET platform. It's amazing how today's tools & technologies can provide "eyes" to the computer & process faces in photos, mostly for free.
Newer versions of the popular photo organizing & editing software Picasa & Windows Live Photo Gallery now have a face detection & tagging feature which finds the people in your photos so that you can add a name to the face. Once you add the names to faces in one photo, the software matches similar faces automatically in your entire photo collection & organizes photos by the name tags.
When Picasa is not sure with the face detection, it provides suggestions that require a manual confirmation.
Also see:
Digital Photography Tips & Tricks
#551