We used five things while Noah was sleeping or we were trying to do something that required hands or no Noah, like showering or cooking:
Crib: We received a crib used from a friend. We did buy a new mattress, which cost about $40. Noah didn't actually use the crib much until recently, so it wasn't something we needed from Day 1.
Co-sleeper container. We had a little co-sleeper thing in the bed with us, because we were scared we would squish Noah- not sure if we'll need that next time, as this really wasn't an issue, particularly in summer when there aren't a lot of blankets on the bed.
Reclining Baby seat, given as a gift. This was really useful when Noah was little and immobile, as it meant we could cook while he watched us. We also used the laundry basket, when Noah was a little bigger. But the baby seat was awesome while he not yet able to sit up.
Baby jumperoo: bought at thrift store for $10, used when Noah was mobile but not super mobile, only so that Eug could shower. Like those walker thingys, Jumperoos are discouraged by baby development specialists, because they can stunt a baby's development, but it was useful for us because it was the difference between Eug being able to shower (I leave very early for work) and not, between the ages of 5 and 7 months or so.
Rocker/Glider: I was surprised how invaluable a glider was for us. We didn't buy it until Noah was about 4 months old, and we realized we were going to be up with him in the middle of the night. A lot. Then we bought it in a hurry and it became our secret Walmart chair ($50 with free shipping...). I really dislike Walmart and wished that we hadn't had to buy in such a hurry.