Whenever I'm torn over whether a thank you note is *really* necessary, Kris Humphries' voice rings in my ears: "You don't want me to resent you, do you?" He was a total psycho, but his caveman voice is motivating. If you're a civilized human being then you have many occasions to send correspondence: thank you notes for favors called in, gifts received, vacation homes stayed in. Also: birthdays, anniversaries, and the disingenuous card you have to write when you leave a job thanking your boss for 'opportunities'.
Don't go for the Rifle Paper cards - they're more ubiquitous than Tumi carry-ons at a consulting firm. You don't want your recipient to think you have the taste of the masses, right? If you take the worthwhile effort to patronize one of the following paperies, you'll have no trouble finding a non-basic, extremely apposite card for whoever you're writing.
[Photo via @goodsforthestudy]