Whatever your partner doesn't know about birthing babies, it's time for him to learn. Because the baby really could come at any time, the first thing he needs to know is how to find the entrance to the emergency room. Beyond that, it's time to look into a tour of the maternity ward at the hospital.
If you have the time, enroll in a childbirth class, or at least check out a DVD about the topic from the library. It'll help your partner during the delivery if he knows the lingo in the delivery room.
He's probably already used to your alternating bouts of crying and elation; now he needs to get used to the idea that you're no longer able to pick up his socks and clean his dishes as quickly as you used to. And who knows? You may just stop doing those things altogether. That's a very big thing for a partner to get used to.
So maybe put him to work on the infant seat: He can practice installing it and stop worrying about the laundry that's starting to pile up on the floor.