(which you can't send via USPS anymore, by the way)
Tyler Cowen links to an old post of his that claims that the best gifts are experiences, such as concerts and travel, not objects like clothes or jewelry.
I won't argue that I recall what I did on my trips to Turkey and Eastern Europe better than I recall the exact items received last Christmas, but I think it sells short the impact of a well selected item.
Clothing and jewelry can be experiences. If chosen with care and respect for the recipient's tastes and interests. Every time you wear a certain well-selected sweater or necklace, it can make you think of the person who gave it to you and to recall other circumstances in which you used the item. Giving someone a well-chosen gift means providing them with something to infuse with memories.