The Seventh-day Adventist Church (SDA) was started by Ellen G. White in the United States of America in the nineteenth century and continues to this day. While holding to many Biblical teachings, there are some disagreements between evangelical Christians and Seventh-day Adventists. For example, Adventists believe in the doctrine of "soul-sleep" and annihilationism for the unsaved rather than eternal concious torment in Hell. For more information see the resources below.
"Seventh-day Adventist Church Profile" by Timothy Oliver
"The Seventh-day Adventists: Christian or Cultic?" by David R. Reagan
"Should We Keep the Sabbath?" by James Borland
Much of the material contained at Ex-Adventist Outreach was written by Pastor J. Mark Martin, a former Adventist minister, who now pastors a Calvary Chapel in Phoenix, AZ.