The Digital Dawg Pound has a created a RFID Front Door Lock that uses inexpensive off the shelf electronics. There is a full listing of all the parts required on their site.
“The project works as follows: When a card is placed in front of the RFID reader it outputs a TTL serial signal representing the card’s unique ID. This is sent to the ‘TTL serial to Ethernet server’ module, which converts the serial data stream from the reader into TCP packets which are forwarded to a specified IP address / port. A custom C# application is listening on the specified port for a tag ID’s and once received will check if they are valid, and if so signal the NET-IOM to turn on a relay wait 2 seconds then turn it off again. The relay is connected to a buzzer, and electronic strike which is mounted on the door frame, and when powered allows the door to be pushed open.”