My oldest niece asked me several years ago to send postcards to her young kids because they don't get any mail. I try to buy cards that are appealing to kids although sometimes I've used the ones from the hotel room. They love the cards, and I'm their favorite aunt (for other reasons, too, but this is one). As my other nieces' kids get old enough to appreciate cards, I send them postcards to them too.

I also send postcards to my invalid aunt. It's a quick way to stay in touch, and she loves seeing all the places I get to travel to.