Everyone has probably said it all but I can't resist.
Disposable knickers, horrible but IMO essential for the first couple of days, everytime you go to the loo you can just throw the whole lot in the bin.
Maternity pads for the first week or so then you can get away with using something a bit thinner.
Breast pads, I use the Johnson & Johnson ones, the cheap supermarket ones give me soggy nipples (not nice).
Kamillosan cream and a savoy cabbage, I ignored my midwife's suggestion to get the savoy cabbage before the engorgement thinking I'll just get it if I need it then had a spend an uncomfortable day waiting for my DH to bring one home from work. For all a cabbage costs have one in the fridge at around day three.
Moses baskets are not essential, I got a nice one this time round second hand (didn't bother with DS1 he went straight in the cot). I wouldn't buy a cot bed if you are thinking of having another child before the first will be finished with the cot bed, you will end up having to buy another one.
Definately agree about buying a new car seat, Mothercare have new ones at a very reasonable price, their own make and Safetybaby, IMO a cheap new one is better than an expensive make second hand, you don't know if it has been in an accident.
Personally think wire framed bouncy chairs are a waste of money, had one for DS1, it was very flimsy and he looked uncomfortable. This time I am using the car seat and a Graco Baby Swing (a bargain just now on Kiddicare.com).
Don't leave yourself short of babygros/vests, but I wouldn't buy newborn, I would imagine most babies would not be too big for 0-3 months. DS2 can go through three babygros/vests in one night (seems to be soaking wet almost every time he wakes for a feed in the night). ASDA are doing packs of seven vests for £8 just now and they have some reasonably priced babygros.
Loads of bibs.
A breast pump, if b/f, although I have not yet expressed a bottle I found that this time it helped me through a bout of mastitis when I found it too painful to hand express (probably not doing it right mind you) to get DS2 latched on. There are always loads of these for sale in our local paper, most of them either unused or used once (it all gets sterilised anyway).
Some means of sterilising, I believe cold water is cheapest but microwave or an electric steam sterliser is much quicker, you'll appreciate how important that is at the time.
Agree with everyone else about the toiletries, you get loads of freebies at the hospital anyway (Bounty packs etc) and I still have stuff left over from DS1 (aged 3.5), don't know what baby oil is for either, I use talc myself but won't put it on either of the kids, I'm afraid however I do have a liking for Johnson & Johnson baby bath, love the smell, but I believe some olive oil in the water is much better for them.
A changing mat, personally do all nappy changing on the floor, they can't fall off the floor. Make sure you have got a travel one for your changing bag also, we have some rather suspect looking mother's rooms in this part of the country and it is peace of mind to be able to use your own mat and you always have it for those park bench/in the car type changes.
Happy baby shopping, it's great fun!