The following sites are run by former Mormons (also known as The Church of Jesus Christ of Latter-Day Saints).
Sandra Tanner runs UTAH LIGHTHOUSE MINISTRY.
Ed Decker runs SAINTS ALIVE IN JESUS.
MORMON RESEARCH MINISTRY successfully attempts to critically evaluate the differences between Mormonism and Biblical Christianity.
4WITNESS.ORG has some excellent information on Mormonism in the form of a series of questions.
THEOPEDIA has an excellent section on evangelism to Mormons.
ALWAYS BE READY has a good collection of articles including a tract that you can give to a Mormon; also, links to online video.
THE MORMONISM 101 SERIES by James White
FREE PDF DOWNLOAD
What to Say to Mormons and Jehovah's Witnesses When They knock on Your Door (free pdf download from Mike Licona)
A DIFFERENT JESUS – this article highlights the Mormon Jesus and why the Mormon Jesus is NOT the Jesus of the Bible.
Are Mormons Christian? by Joe Carter (Gospel Coalition)
'Mormonism and God: A Philosophical Challenge to Mormonism' by J.W. Wartick
'How Did Mormonism Originate? Part 1' by Bill Pratt (Tough Questions Answered)
Sandra Tanner, in 2007, discusses her reasons for abandoning Mormonism for Jesus. As a direct descendent of Brigham Young, she is a 'gutsy Christian woman'.
For those who like cartoons ... this is Mormon beliefs in a nutshell.