I accompanied Denise on a business trip recently, and was embarrassed to find that my stash of business cards was woefully out of date. I ordered two new batches as soon as I got back home. I used Moo.com, which has one template that allows you to print as many as 50 different images on the backs of your cards. Which is a great opportunity to showcase book covers!
I don't know about other authors, but when I meet strangers the conversation usually goes like this:
"So what do you do?"
"I'm a writer."
"What kinds of things do you write?"
And that's where it breaks down. I typically end up verbally describingthe types of books I've done, and if they ask for a card, I end up giving them my old outdated card, and a few other old, publisher-printed cards depicting the covers of one or two of the books we discussed. (Denise sidesteps this issue by merely giving them a bookmark for The Girls of Atomic City.)
The new cards allow me to show them them the covers, describe the books if we have time, and then say, "Here—take your pick."