Food. I packed some cheese sandwiches. Nice and simple. It's hard to know what you may fancy when in labour so try to keep it plain. During the early stages of labour, when being checked at the hospital, it ran over dinner time so was very grateful I had packed something filling. I also packed some dried fruit, nuts and seeds, as recommended by lots of pregnancy guides. However during labour you become very dehydrated and its quite hard to chomp down nuts and seeds so would recommended just taking the dried fruit. With hindsight I would pack soft sweets such as haribo which are easy to chew and keep your sugar levels up.
Drink. The hospital provides cups of water, so bring a sugary drink such as fruit squash. It is really important to drink and keep hydrated during labour. Pack a bottle for your birth partner too, he/she will be exhausted as well.
Chargers for you mobiles. My partner phoned our family and friends with the good news, and also kept everyone updated during labour. You don't know how long labour will last, so pack a phone charger!
During birth whatever outfit you've planned goes out the window and you end up in a not so glamourous hospital gown. It is in the early stages of labour when you are at home when you need a comfortable outfit. I had some loose back maternity pants from gap (in fact I lived in these towards the end of pregnancy).
A nursing bra (get measured properly! I recommend the M&S twin pack nursing bra with clips.) is essential with you going home outfit, which (if breastfeeding) needs to be easy to either unbutton or lift up. Don't worry about breastpads to much yet, the leaking is yet to come... Remember, you will still be in maternity wear for quite a while (very disappointing I know). Pack a couple of pairs of underwear (comfy and large) and some socks for walking around in the hospital. Along with slippers and a comfy dressing gown. If you have an easy birth and you are eager to return home with your new family, then you may not need to stay in the hospital overnight however it's best to pack some nightwear just in case. Pack a spare outfit for you birthing partner too.
Toiletries. If staying overnight a toothbrush for you and your birth partner, toothpaste, shower gel, shampoo and conditioner. Anything you usually use for a shower. A nice towel and hair towel. Most places allow your partner to stay overnight with you and they can help you shower the next day so pack a towel for them too! Take a hairbrush and hairbands too, you will really want your hair out the way! Maternity pads. Lots of them. Big ones. After birth you bleed for anywhere up to six weeks, although most women only bleed for around 2 weeks (even if you've had a cesarean). You need to change your pad every hour for the first day after birth so stock up!
Your camera! with a full battery and lots of free memory. That way you can capture as much or as little as you want. I love looking back at photos of Poppy's first few hours.
Change for parking. Hospital car parks. Enough said.
For baby. Size 1 nappies and baby wipes. The hospital will probably provide and put on the first one, after then its up to you! A baby vest (newborn size), and a babygrow (newborn size), bring a couple of each. The hospital will also provide blankets but its nice to bring your own (especially if home knitted). Everyone recommends a hat and scratch mitts. These fall off within a matter of minutes so I would just bring one of each. And finally a nice going home outfit for your baby, (which needs to fit in the car seat). We had some nice knitted booties to keep her feet warm over the top of a babygrow (and vest) with a matching hat. Muslin square, useful for everything baby related.
Extras: music for you i-pod, swimsuits if having a water birth, makeup for the glamourous mums out there.
I hope this post was helpful, if any mums had some essential items they would like to post that would be great, any advice is welcome.