I highly recommend the Pocketbooth app for a smartphone (or at least the iPhone). And I've always loved those little coin envelopes which really don't have much purpose, but boy are they cute. Just snap, print, cut out, fold, tuck into envelope. I actually then used double-sided tape to stick the little silver envelope onto a larger piece of cardstock, and wrote a note around the edges.
Hm, I may have to design a freebie based on this. It wasn't the least time-consuming card I've ever made, but it just might be the cutest. Well, a fat baby always helps up the cute factor.