The Encyclopedia of Mormonism is now online at BYU.edu. This is a helpful resource with an extensive list of entries related to the beliefs, teachings, and practices of the Church of Jesus Christ of Latter-day Saints.
Learn more about the Encyclopedia of Mormonism at this link.
This online edition of the Encyclopedia of Mormonism is a PDF scan of the printed set of 4 volumes. It does not include volume 5 (which is the text of the scriptures) because the scriptures are available online at scriptures.lds.org. This PDF edition has been indexed so you can enter a term in a search box to find the entry. The full text cannot be searched until next year, when the full text will be put online and will be completely indexed.