Sounds like you've got a keeper! We're sure you can think of one or two or a hundred ways he can help you out, but if you're having trouble getting started, print out these tips — sure to help most any relationship — and pass them along.
[ ] Don't take your wife's mood swings personally — it's not you, it's the hormones. (Sound like a feeble excuse? Forget the hormone thing, then. Just consider how you'd feel with a small person growing in your belly. Okay.)
[ ] Pick up some books on pregnancy. Your wife's body is doing some wacky things — she'll feel much less alone if you've got some idea of what's going on. Plus, you'll score major points every time she sees you with your nose in a book about babies.
[ ] Have as much fun (as a couple, of course) as you can right now — your social life will never be the same. (No, we didn't say worse. Just...different.)