There is a huge variety of iPhone cases on the Internet and in the classic stores, and you can find many hard, slim fit or silicone cases. Some people would like to cover everything, but some others would like to cover only the sides and the back. As long as the controls and the ports are accessible, I would like to cover everything, for a better protection, but many producers find it easier to create the standard with less protection.
A very interesting case is EcoShield for iPhone, from Agent 18, which is a plastic case made from recycled materials, which is created on the principle "protect and conserve". It has two versions, in black and natural, and it is a two pieces case: a tray for the iPhone and a small piece which snaps over the front, to close the case. The screen is not protected, and it allows access to the dock connector, volume and camera. One of the cool things at iPhone 3G is the sleekness, but with this case is lost, and because of the fact that the thin piece snaps on, it allows dirt to get in the case and under the edges of the case. This is a bit gross, to see dirt gathered in the case of your iPhone. It is a solid and ecologic case, but you should study it a little, before buying it. It costs $25.
iLuv Silicone Case for iPhone 3G is made from silicone, a strechy silicone which allows iPhone to get in and out of it pretty easy. It is tacky and you can grip the phone in more safe conditions than in a plastic case, or even without a case at all. The case allows access to the camera, headphones jack and to the dock connector, and the case is so thin that you can use the volume and home buttons, even if they are covered. The most important aspect is that the screen is uncovered, and this might be an disadvantage, but as I said, not many people prefer "cover everything". Another disadvantage would be that it attracts lint and it is hard sometimes to take it out of a pocket or put it in.
DLO Jam Jacket case for iPhone is a good product, and besides the protection offered for your iPhone, is has a small section on the back, for storing the earbuds and their cord. You can wrap the earbuds and the cord around this section and there are two divots for the earbuds, where you can fit them. You can charge the phone while in this case, but you cannot use the dock connector because the case doesn't have the extra room for it. I personally don't like that this case didn't allow me to access the camera, the dock connector and the proximity sensor, but I appreciate the protection offered to the smartphone.
You can choose from the large variety of iPhone cases, but the most important thing is that the product you purchase must fit your needs, the price and the quality you expect from it. A phone case is very important, whether it is to make it easier to hold, or to protect it from scratches on the back or sometimes on the screen and you should know that a hard case will protect the iPhone when you drop it, because it offers maximum protection, skin cases let you to keep the slim aspect of your iPhone, protects against scratches and it comes in a variety of colors. A simple flip lid will allow you to protect the screen and easily access the interface features by flipping the lid.