You can get way too much good hammock information at
http://www.hammockforums.net/. A lot of the hammock campers there seem to be backpackers, too, so they don't take a single ounce they don't need.
For my part, I got a good deal on a Hennessy Hammock last spring, probably something like 33% off, so under $100 for the cheapest model. You can find cheaper options, and you can find DIY options, but I love my Hennessy. My first night in the hammock, I climbed in, got settled, and thought, "This is cozy, but I wonder if I can really sleep in---zzzzzz." It was the best night's sleep I had ever had camping. Hennessy Hammocks are made so that your feet go off center in one direction and your head in another, so you're lying more flat then on the curve of the hammock.
Mind you I only have half a dozen night's experience in my hammock, but I was converted after the first night.
Pros- No ground sheet needed
- No ground pad
- With the fly adjusted right, you cannot wake up wet
- No poles
- Comfortable
- Packs small
- Lite (at least compared to any other tent I've carried)
Cons- If you can't tie it up (no trees, for instance), and you didn't bring any ground-specific alternatives, you may have a rough night.
- You get chilly quicker with airflow above and below. There are many ways to deal with this, but all of them add bulk.
- One person per tent. I've heard of some heavy duty, two-person hammocks, but most people find them uncomfortable for sleeping even if they can take two people's weight.
- Cannot take your gear into your tent with you (at least not much of it).
Like I said, I don't have tons of experience, but after my first night I was convinced that I never wanted to sleep on the ground again.
Lots of pillow options. Some folks just have a small pillowcase or other sack that they stuff some spare clothes into for minimum added bulk. There are also small, camping pillows, some that inflate, so they don't take up much space when you're not using them. For hammock camping, there are even camping pillows that hook to the end of your hammock, so that they don't drift down to the lowest point of the hammock while you sleep. My default had been a wadded up sweater, but I'll probably get a real camping pillow soon. I still like something under my head, but in a hammock, your head is often already a little higher then your midsection, so it doesn't seem as important.
Tarps: I know I was preparing to drop some money on a decent tarp for my hammock, but I really didn't want to, so when I saw
this on the hammock forums, I jumped on it. Haven't tried it yet. Might be larger then what you need, and therefore heavier then what you want, but you also might be able to cut it down smaller. Hennessy hammocks come with a rain fly, but I worry that won't keep rain out if it gets really windy. Plus a bigger tarp might be large enough to cover my bike and other gear. And this tarp seems like it might be a good, general-purpose tarp, no matter what your tent situation. Also it's white, so not a great stealth option, but if you're looking to cut costs, it looks promising.