This site gives a simple list of the Twelve Imams along with the Prophet Muhammad and Lady Fatima as the Infallible people revered in Shi’ism. There is also a brief description of the first three Imams, Ali, Hasan, and Husayn as greatly respected helpers of the Prophet.
This article gives a detailed description of each of the Twelve Imams, their significant accomplishments, and their deaths. There is also more information on the Shi’a traditions and beliefs about these important figures. This information only includes the Twelver Shi’a line of succession without reference to the other off-shoots.