Here is a video from youtube, all about the lost art of the Thank-You Note. I love the idea of having a Stationery Wardrobe. And a stationary wardrobe too; although, I think most of us have one of those already.
Other Etiquette Tips
(from Elizabeth Mayhew)
*** When you receive a gift from a number of givers, you must write to each person separately, unless of course the gift was from a family or a collective group of coworkers. In that case, you can address the givers collectively and request that your note be circulated or posted.
*** Sometimes a thank-you note is not enough. If a friend goes out of her way for you, or friends invite you to be their houseguest for the weekend, then you need to give more than a note.
(Think wine, giftcard, dinner, reciprocal arrangement.)