There was a fabulous thread somewhere on BB asking the same question with lots of comprehensive lists from lots of people. I just searched but couldn't find it, but I'll continue to look and if I find will drop back in and advise.
Some of the things I remembered from others advice and have packed for myself were:
Lip balm
Hair ties
Food (cuppa soup, bikkies, lollies, muslie bars etc)
Energy drinks
Socks (apparently feet can get very cold)
Change of cloths for partner for when he/she gets wet in shower/bath with you
Swimmers
Maternity pads & Breast Pads
Music / essential oils / inspiring photo's
Dressing gown / slippers etc
Rescue Remedy (I never leave home without it)
List of those who need to be contacted after the birth
If I remember any others I'll come back.

Best of luck to you.