To thank someone for something small.Sincerity is a lost art. Practice often.

To say “Happy graduation.”

Welcome to the real world.

To say “Sad graduation.”

Welcome to the real world.

To congratulate someone on getting their driver’s license.

No texting and driving. Always best to send a card.

To celebrate a new year.

Let’s make this year better than the last. And then let’s do the same next year.

To congratulate someone on getting a puppy.

They make edible cards, right?

To congratulate someone on getting a kitten.

They have years of being ignored ahead of them, so why not give them a little attention now.

To welcome a baby into the family.

In about 18 years they’ll have time to finally read your card.

To “apologize” for not inviting someone to your wedding.

It’s tough. A little thoughtfulness now can save a lot of awkwardness later.

To offer a random compliment.

Fact: 100% of people enjoy receiving compliments. Fact #2: Your hair looks great today.

To say, “Look at this gorgeous card I found.”

Don’t keep something that pretty to yourself.

To congratulate someone on a new car.

Butter them up for when you inevitably ask to borrow it.

To celebrate Thanksgiving.

No one sends “Happy Thanksgiving” cards. Be unique.

To celebrate the Fourth of July.

If they’re American, it’s sort of a second birthday card.

To congratulate someone on a promotion.

If appropriate, maybe include your résumé.
Copied from http://www.howlifeunfolds.com/stronger-connections/100-unconventional-reasons-to-send-a-card
Great post