I recently finished hacking apart a Keurig coffee maker, adding an Arduino for controlling it from a netbook and an RFID reader for authenticating users. I did a full write up. See the youtube demo here:
That is impressive project using RFID. I wonder... it is for the office ? That will be the application for a RFID, because you want only a few selected co-workers to access the coffee maker. At home application... humm... wife, kids ...nah .. more for the office.
Well done. And ... You could make it Computer independent if you add an LCD to show your text. You could also use sd-card for keeping data and use the ethernet shield, so you have a network connection to check data stored (or go for and Arduino Ethernet)
When i read the Subject-Line, this idea came into my mind:
A Coffee Maker (the one where you can select between cuppucino, coffe w/ milk, milk and sugar, ...),
which automatically brews your preferred coffee if you place your mug (with RFID-Tag on the ground) on it.