Organ donation is a tremendous act of kindness, and there is a great need for organ donors of all ages. In fact, there is no age limit. Even if your liver isn't in good enough shape for donation, perhaps other organs and tissues could be used by someone else.
Here are examples of organs, in addition to the liver, that can be used: heart, intestines, kidneys, lungs and pancreas. (Forgotten where these organs are located and what their functions are? Take a quick tour of the digestive system.) In addition, certain tissues can also be used: bones, corneas, sclerae, tendons and certain veins.
There are, however, diseases that will prevent organ donation. Examples of two relatively common diseases include being HIV positive and having actively spreading cancer.