I'm sitting here trying to think of all the things we make sure to take with us when we travel we seem to do it a lot. Trips anywhere between 5days+ or just over nights and I know it sometimes takes me forever to remember it all so I will try and maybe someone will find it useful. Good Luck
Feeding
bottles
nipples (enough for the bottles and a couple spares)
formula and/or pump
bottled water (so her tummy doesn't get upset with different water)
steralizer
thermos (so we always have hot water - fill it at the coffee shops)
measure cup (for mixing powdered formula)
liners if you use them
Clothes
Sleepers - 1 per night plus 2 extras (in case LO spits up at bedtime)
Outfits - 2 per day (packed in sealable lunch bags ie. ziploc helps keep things fast/easy)
and any socks, shoes, hats, mits, bibs that you prefer they wear
Misc.
receivers - 2 per day and 2 extras
blankets - 2
soft toys - 2 (in case 1 gets dirty/spitup on)
teetherish items - 2
soothers - minimum 4 (they get lost and dropped!)
infacol - or other gas meds
gripe water (helps with gas too)
teething gel - if you use it
thermometer
soap (for the bath)
baby towels - 1 if you use them
wash cloths
diapers - I allow 8 per day and usually have a couple left over
wipes
bum cream
plastic bag to keep dirty clothes and clean clothes seperate
baby sling (or what have you if you "wear" LO)
If space permits...
stroller and playpen/cot for sleeping in
If you have laundy facilities bring your baby laundry soap too! I've found you can't always get the same products everywhere and it will help to cut down on the clothes you need to bring
I tried to remember as much as I could will add things if I think of more. Have fun on your trip