In New Orleans a couple of weeks ago, when we took the kid to her first dive bar (We were told it was a restaurant and... long story. But it was lunchtime...), the bartender's t-shirt told me he probably knew his customers better than they knew themselves: "Just because you can reproduce, doesn't mean you should."
That same advice could apply to making up some t-shirts (umm, mea culpa), or to blogs, for that matter (mea culpa again). It's just so damn easy, and everybody's doing it now, that when you find a really good one, you should really stop and take notice.
Wry Baby is one of the good ones. In addition to being clean and unfussy, their designs have just the right amount of humor for a baby snapsuit (which, in a trademark-free universe might be called a Onesie). It's the difference between someone who's naturally funny, and that dork in the back of the room shouting out jokes all the time. Other designs are just plain nice.
Some favorites: "I'm not a boy." (which must outsell "I'm not a girl." 10-1); the "Lifting Baby" schematic; "Chalky Tasting Formula/Science makes it bland!"; and "I heart my dads," for the fellas. People magazine likes "I might barf," which is the un-wry-est one. Go figure.