According to the U.S. National Safety Council, you should have smoke detectors, and at least one fire extinguisher available in your home, to help prevent a fire-related disaster.
For the kitchen, an all-purpose extinguisher is a great idea. It can combat both grease and electrical fires.
Other locations to keep fire extinguishers: in the garage, near the furnace, and wherever else that something combustable has the potential to start a fire.
Be sure that everyone in the home, whomever is able-bodied, is familiar with the use of fire extinguishers as well as where they are kept in the home. They will not help if no one knows how to use them.
Update: Fire Safety Training is now available.