In mine I currently have:
* 5 nappies
* travel wipes
* nappy bags (for used ones)
* sample sized nappy cream
* full change of clothes (including singlet, socks)
* beanie (and in summer a hat)
* change pad
* muslin wrap to cover up when breastfeeding
* aquim handwash
* 2 dummies even though she rarely uses them
* cloth nappy for vomit catching!
* wallet, keys, phone
* bottle of water for me (breastfeeding is thirsty business)

We have a blanket permenantly in the pram basket so I don't need to pack on into the nappy bag each time.

I always restock it as soon as I get home that way I know it's ready to go as soon as we are. It's much easier to keep it packed & ready.