Hammock
Hammocks are a big category within the camping world. This is largely due to how much people want to use their hammock. Many people actually camp in their hammocks, no tent, just a hammock. Others use it for lounging around.
The first thing to pay attention to with hammocks is the size. Typically there are singles and doubles. Singles have a width of four to five feet, although that sounds like a lot, most hammocks don't lay flat, they come up on the sides, so a single isn't really one that will allow you to roll around. Double hammocks are five to seven feet wide. These are a bit more roomy. Lengths are less standard and you will want to check them especially if you are tall. You should leave at least two feet of space. So if you are six feet tall you should be looking at eight foot long hammocks. If you are over 250 pounds you want to watch the weight capacity as the lighter versions tend to be close to the 250 mark.
If you are going to use your hammock as your tent, bed, everything... You will need more than just the hammock itself. You will want to consider warmth, rain, and bugs. You can buy hammock systems that contain all the necessary parts, but the right one for you may not.
If you are sleeping in a hammock in the cold you will want an underquilt, these are a type of liner that creates a bit of insulation and reduces air flow through the hammock material. You also will want a rain fly, unless you are positive there will be no rain. These are similar to tent rainflies which are suspended above the hammock to keep you dry or block the sun. Depending on where you are in the world, a bug net may be the one thing keeping your sanity in a humid environment. Some bug nets enclose the entire hammock while others can be zipped onto the hammock directly, these are typically a part of a combined system rather than an add on. Remember that a "no-see-um" netting will keep out the gnat sized pests as well as the larger ones that can't fit through the net.
The last thing to consider with hammocks is the suspension system. As most people will imagine a hammock tied to trees and this is the most common suspension system. This is done with tree straps and carabiners that are rated to hundreds of pounds. These will typically will come with the hammock. You will want to be sure the strap is at least 0.75 inches wide to be sure not to damage the trees they are tied to. But, if you want to hammock camp in the middle of the desert where there are no trees or your campsite is completely cleared... The other option are hammock stands. These are made for lounging and to put in your backyard. They are bulky and heavy, but could be an option if you are car camping in a place with no trees.