How about a coupon book you make up yourself, with a parking map for the hospital parking lot (put a "redeemable on X date" block on it, using your approximate due date). Then put in a job list, including things like "clean closets in response to nesting instinct" or a grocery list with whatever your cravings were before (or what you think they will be). Or you could do the stereotypical things: sardines, ice cream, pickles, saltines, ginger ale. Then a couple of catalog sheets or on-line printouts/sources for the things you'd like - pregnancy pillow, rocker, crib, and so on. You could put things on a calendar (things like "ultrasound" or "Monthly" or "weekly checkups", or you could make a bulletin board of all of the above and just put it in a place where he'll see it. Don't say anything - just wait until he sees it. If he's really dense, you can say, "Honey, is there anything on the calendar for February 20th?" or whatever date you've entered something in.
Have fun!