This project, which I call FRAMS(Face Recognition based Attendance Management System) was built recently by me as a proof-of-concept application, for one of my clients in Educational sector.
This project enables marking attendance of students by their faces (thus eliminating chances of proxy attendances). The project provides an Admin section, where Administrators can enroll students with their sample face images (currently 5, but configurable). These images can be clicked directly from the application by attaching a web cam to the system. The application can recognize all web cams including the ones that come with most laptops today.
A student then needs to get his/her attendance marked by getting his/her image clicked by the application daily while entering the premises. The application ensures that each student's attendance is marked only once daily, no matter how many times he/she faces the camera in one day.
This application has been built in Java, but can be easily ported to .NET or any other platform. You would need to install JMF (Java Media Framework) separately before you can run this application.
More information on this project is available at this blog post.