1. A two-person tent. Just for me. This leaves room for all my bits and bobs. Always buy a tent that sleeps more people than you actually want to sleep in it. I swear. Mine is a three-season tent from Sierra Designs that has stood up well to the occasional downpour and even a couple inches of snow on one memorable May morning. I like a vestibule so I can stash my shoes in it and keep my tent tidy inside.
This little fella has done ok over the past four years, the zippers tend to stick but it's roomy and comes with a rain fly that works like a charm! Great for unexpected downpours! Also, it was on sale ;)
2. A good inflatable sleeping pad. I swear these are a worthwhile investment, which I am reminded of every time I pack up my tent and realize that I was sleeping on a pine cone all week. Mine is not the poofiest but I am more of a back sleeper and less of a side sleeper so I don't mind as much, if you are a devoted side sleeper a poofier pad is your best bet since your hip will be digging into it. But I had a non-inflatable foam pad early on and it just doesn't do the job.
3. A cozy sleeping bag. Nuff said.
Edited To Add: after four years of hard use and infrequent washing, this sleeping bag has finally had a seam open up in an interior corner. It was a bitch to sew up as it was three-sided but I will see if it survives. The rest of the bag is in great shape.
4. Lighting options. I have a little flashlight that extends and makes a little lantern that I can hang from my tent ceiling. Normally I use a headlamp but when in a tent trying to take your contacts out a headlamp will make an unfortunate (and blinding) glare in your little travel mirror. So I have two lighting options that I travel with, and our crew has a bigger communal lantern that lives in the cooking area. It may attract bugs but can be helpful for late-night Cranium games when headlamps would blind your teammates.
We carry a lot of communal gear like folding tables and chairs and propane stoves that make life a little more comfortable out there. But these are my camping necessities. When I camp with Matt we take his VW bus so I don't need most of this stuff but I sure am glad to have it when I am out for a week at a time for work.
What are your camping necessities? Do you like to car camp, backpack or just stick to a nice hotel?