Corporations and many other businesses can use this type of letter as a precursor to a formal agreement. In it they can list the salient points of their intentions and what they intend to include in formal contractual agreement if both parties can come to an amicable agreement. Thus it can be used as a fall back document should any questions arise during the final contract negotiations. A good example of this might be a letter sent to a company's investor explaining their intentions to buyout another company and what it is expected to do to the value of their stocks.
Academic: In the academic world a letter of intent is known as a Statements of Purpose and is part of the application process. Real estate: Often times there are properties that are not listed on the MLS or with a realtor. It is at these times that a letter of intent can be used to let the owner of the house know that a potential buyer exists and thus the process of buying and selling the house may begin.