The bag!!

Actually, that should be plural! You need a bag, Daddy needs a bag, baby needs a bag, and then you need one for all your extras for your stay. Of course, these can all be combined, and probably should, those hospital rooms get small quickly. As for when to have them packed and ready, your doctor will tell you when he/she thinks it's time, but I think a good time frame is a couple weeks before your due date. Then again, after 37 weeks, they say you could go at any time, so if you feel more comfortable having them ready earlier than that, go for it. I have just under 4 weeks before I deliver, and even though it's a C-section and there's very little chance I'll go into labor before then, I'm kinda feeling the need to have it all packed, so I'll probably be getting mine ready sometime next week. (Holey Moley, next week!!)
I think it's a good idea to pack a "just in case" bag, or add some things, just in case you have a c-section. I've read that 1 in 4 deliveries ends up being a c-section these days. The average stay for a vaginal delivery is 24 hours, but is 3 days for a c-section, so packing a few extras in your "just in case" bag will be helpful. You'll need a lot less than you think, though, just like everything else when it comes to a baby.

MOMMA'S BAG:

• your regular toiletries (toothbrush and paste, shampoo and conditioner, deodorant, facewash) and don't forget hair and makeup stuff. You won't feel like going all out, but when looking at the pictures later, you'll wish you had at least thrown on some mascara... at least that's how I felt. I'll be spending a little more time this stay blowdrying my hair (or having someone else do it) and putting on a little bit of makeup.
• 2 or 3 good nursing bras and/or tank tops
• socks, those rooms are freezing
• the hospital provides some lovely mesh underwear for afterwards... hideous, but soooo comfortable, so bring your own, but you might not need them
• comfortable, fairly loose fitting pajamas
• "just in case" you might prefer gowns if you've been cut. There are a couple reasons for this: the first is that pajama pants might be uncomfortable on your incision. The incision will probably be very low, and the pants wouldn't fit directly on it, but it still might be very painful. The second reason is that you will have quite a bit of discharge afterwards, called lochia, that you didn't get rid of by vaginally delivering. Your postpartum nurse will come in every few hours to massage your uterus (or torture you, however you want to look at it. Seriously, it hurts!) and make sure that you're still discharging and it's not clotting. This is much more convenient and goes much quicker if you already have a gown on.
• house shoes, flip flops, etc. for walking afterwards
• sanitary pads... the hospital will provide some of these, but you might prefer your own brand and absorbency. The ones they have could be used as diapers.
• Your going home clothes. It may just be me, but I like to dress up a little bit. Some women just want to wear pj's home.

BABY'S BAG:

• you could include baby's stuff in one of your bags, but you probably just got at least 5 super cute diaper bags, and you've got to break them in sometime!
• the hospital will probably provide everything you need for the baby, including diapers, wipes, any creams you would need, etc. and you usually get to take home anything left over.
• comfy little outfits for baby to wear during your stay, nothing fancy, the baby will sleep for the majority of the first few days. And remember, it's likely that baby will ruin at least 2 outfits a day for the first several months, and it could start that very first day (especially with a rookie dad handling diapers!) so don't bring the whole closet, but 4-6 outfits would be plenty.
• receiving blankets for the ride home (unfortunately, the hospital doesn't let you take those, even though they are the PERFECT size for swaddling)
• the car seat (obviously, but I know sometimes it's the details I concentrate on and forget about the obvious stuff)
• the going-home outfit! and be sure to take pictures of him/her in it before you put them in the car seat and before you get home. Complete outfits have a way of becoming incomplete during a car ride, no matter how short!

DADDY'S BAG (and all the extras):

• Daddy can take care of his own clothes and toiletries (you have enough to worry about!) but remember the possible extra couple of days.
• cell phone chargers for all those calls
• a pre-determined, written out list of people to call
• camera, video camera, all applicable chargers, and plenty of memory cards and tape. Triple check these! Make sure everything is charged and that you have a fresh tape in the recorder and an empty memory card (or two.)
• if you want, a baby book for all your guests to sign. I also suggest that as soon as you get a gift or flowers while there, you have someone write it down in the book. We just kept cards in an envelope, but when we got home and were ready to write thank you cards, that envelope was gone, and we had no idea who had sent what.

Come on, gals, what else can you think of??