One company I worked for used the Philips MiTAG rfid and had to sign a NDA to get access to the software. As I wasn't involved in that project ,I never saw the code. Nevertheless is was not simple.

My suggestion would be to purchase ready made RFID boards that get around the whole issue of NDA etc. The ones I've seen use serial to communicate - when they detect a rfid tag, they output the device number. Try http://www.adilam.com.au - I think they have both the readers and the rfid tags.

Otherwise try Google.