Ahh, you must know I've been watching Heroes this summer, so superpowers are very much on my mind.
It's a hard call, you know? There are so many cool options: mind-reading, healing/regeneration, walking through stuff, telekenisis, flying, invisibility, persuasion (being able to talk anybody into anything), breaking the time/space continuum (hey, a gold star for anyone who can give me another word with a double U in it!)...
I know I don't need super hearing, super strength, laser eyes, or the ability to blow stuff up. Super speed would have it's uses for a mommy, as would the stretchy-skills of Mr Fantastic (or Elastigirl, but hey, Mr F came first).
Just the other day I thought of a great mommy super power: the ability to always know when one of my kids needed to go to the potty. How great would that be? I mean, toilet training would be a breeze, and we'd never have dirty underpants or wet beds. Even the wait-till-the-last-possible-nanosecond-to-sprint-for-the-bathroom syndrome would be nipped in the bud if mom knew to tell the child to go.
I can think of some other great mommy superpowers, like the ability to make everyone always tell me the truth, or to know precisely when it was going to rain (so I could plan my walks around it).
Frankly, I think that the superpower I DO have (making milk) is pretty darn groovy. But I know that's not in the spirit of the question...
...and in the spirit of the question, unoriginal as this answer is, I think I have to go with teleporting.
(Pssst, Did you think of another double U word? The only one I can think of is vacuum. Weird lookin words though, aren't they? Continuum and vacuum?!)