Hello S.! I was overwhelmed with what to buy my little baby boy (Born 8/16/07) too! Here's my advice, which pretty much echo's alot of the other responses:
Onesies are a staple item-have lots of them in a range of sizes! Don't buy too many of the newborn size because you'll notice babies aren't in them for very long (unless they're preemie). Carters are awesome and the Gerber white organic onesies at Target are great and REALLY soft!
The little cotton pants that match the Carters onsies (you can buy them as a set or separate, especially at a Carters outlet if you have one nearby) are great! While baby jeans, khakis and overalls are really cute, they're not completely practical because they take way too long to put on (and take off when changing a diaper). Anyway, you can buy the little cotton pants at Carters, or even at Target. I used them ALL the time with my little one...we found we didn't have too many cotton pants when we brought him home, so we took our first trip to Target and bought some that matched some of his onesies!
The gowns are great for newborns because you just lift them over their little bums when changing late night diapers, and then lift them back down when you're done!
Get a few hats for the baby to wear...cotton of course. Gerber carries them, as well as Carters.
SOCKS-stay away from the cutsie socks that fall off/roll off, which can be hard to spot, but generally are the tiny ones that don't have a decent grip at the top. I found great socks to come from the GAP, and those cute Trumpette socks that come in Camouflage (for boys and girls) and cute Mary Janes for girls.
The zip up cotton pajamas are great for night time. You'll see lots of snap ones, which are good, but can be cumbersome when changing a late night diaper(s) and you're not 100% awake yourself. Zip up PJ's are faster. Get them at Target and Carters. My first recommendation would be CARTERS! Because they have really soft cotton and flannel ones!
Last, but not least: Bring a couple comfortable "take home" outfits to the hospital. The first outfit we put our little boy in got messed. Thank goodness we had another.
I'd also recommend the MIRACLE BLANKET for swaddling. It works. Trust me. And I didn't have it when my son was born. I got it at about 7 -8 weeks old. Let's put it this way, my son went from waking every 2 hours to waking every 5 hours after placing him in the Miracle Blanket. It can take the baby a couple days to get used to...
Oh, and the HALO Sleepsacks are great too... but you can't swaddle with them unless you buy the Swaddle Halo Sleepsacks.
ALSO if you're using disposable diapers: ONLY buy the PAMPERS SWADDLERS! They are by far the best diapers! If you get any other, exchange them for SWADDLERS.
OH, also...get lots of cotton diapers for spit up rags (I's recommend the colored ones because you'll be able to find them late at night better than the white ones)...and burp cloths (gerber) to use for nursing. I put them under my breast while nursing so I would get milk over my shirt and bra. They're lightweight, not as bulky as using a cloth diaper. Nursing can be a little messy.
Best,
M.
(Mom of a 3 month old)