If you are looking to do a complete kitchen remodeling for yourself, or for maximum resale value, don't neglect the kitchen island stools. Once just a place to pull up some stools so the kids could eat before running to the bus, the island and it's function in the kitchen has changed quite a bit in the last 10 years.
In addition to seating 4 (or more), islands today are used to house "luxury" appliances that do not fit in the cabinet structure like a second microwave, second oven, wine refrigerator or even another cooktop. Islands many times are fully wired for electricity and have plumbing for a second sink. The base of an island can be used as a wine rack. The possibilities are almost endless.
We are often asked if the countertop of the island needs to match the existing kitchen countertop in style, or what will be installed as the main kitchen countertop. In most homes I would say it does match, but it really does not have to at all, nor does the material need to be the same. In fact, if you are not going to match them up exactly it's better if it looks like you are not even trying to match them, so using a completely different color and surface is perfectly acceptable. For example, we have seen islands of concrete when the rest of the kitchen countertop is made of granite or another material. We have seen a black island used as a nice "dividing wall" to keep the kids away from a white kitchen.
What can we expect to pay for an island during a remodel? This one is too hard to answer because there are simply too many choices. A "ready to install" stock island you can purchase in a home store with connections for drainage and power can run about $800. A custom concrete countertop island with sink, cooktop, and wine refrigerator can easily eclipse $10,000.
If you are not looking just for resale value, and we assume many of you will actually want to use your island, just think if the main uses for the island before construction. Will it be a place for the kids to eat breakfast or a baking center for your wife who like to make pies and cakes? The design should really follow the function when it comes to an island. For example, if you are tired of not being able to put hot pots directly on your countertop, install granite on your island, where placing a red-hot pan should be no problem.
Plan the height of your cabinet appropriately. Since most islands will have at least two stools or chairs pulled up to the surface, you may want to think about the seating or stools first. There are two kinds of island stools with one being much higher than the other. Unless the island will be used primarily for family eating, there really are no hard and fast rules on height. It does not have to match the height of the kitchen cabinet, but often does. If it is not going to match it should be taller in most cases.
Islands can "float" as well. Smaller islands used primarily as an aid in cooking or baking can be fitted with wheels and moved around the kitchen as needed to aid in cooking. Whether you consider a floating island will probably depend on what you have installed on the floor now, or plan to install (a soft wood will be nicked and scratched).
For those remodeling and looking for an "open" feel where perhaps the wall or half wall separating the kitchen and the dining room is taken down, a strategically placed island acts as a subtle room divider mentally separating the kitchen from the dining room but with a much more open feel.