I send holiday cards to keep in touch with old bosses, who I might want to use as a reference and co-workers I want to keep in touch with. It isn’t strange to receive a card around the holidays, so there’s no need to feel weird about it.
As for the advice from Vickie Elmer (the post author) to send a card to those you have interviewed with, I think this is a tread carefully situation. If you are still being considered for the position, I say go ahead. If they turned you down, but encouraged you to apply for another opening, send the card. If they simply cut you lose, think about how much you really want to work for the company.
Sending a holiday card is especially important for soon to be graduating students. A holiday card is a great way to remind that internship director of who you are and your impending graduation. Just think carefully about your wording. If it seems awkward to write, it will be awkward to read. Less can be more in this situation.
Read Vickie Elmer’s article. It’s full of great tips.