We at BYU Studies are big fans of resources at the LDS Church History site, https://history.lds.org. Here is a list of just a few of our favorite pages.
Revelations in Context "contains stories told from the point of view of those who experienced the revelations in the Doctrine and Covenants, giving us insight into their meaning. While the section headings provide context for the revelations, they don't tell the complete story. What questions prompted the revelations? What did the Lord's responses mean to those He addressed? How did they respond? Perfect for study with the Doctrine and Covenants." The full book is available online, and a print version is available for $3.45.
Foundations of Faith offers a tour through Church history from 1829 to the present with photos, artwork, documents, and videos of selected interesting places and events. See the Book of Abraham facsimile printing plates (1842) and President Hinckley's preliminary sketch of a small temple floor plan (1997).
Lecture Highlights and Pioneers in Every Land. Here are videos of lectures given in Salt Lake City sponsored by the Church History Library. You can watch "'That They Might Not Suffer,'" by Sharon Eubank (2015), "Learning to Listen: The First Integrated Branches in South Africa," (2017), and many more.
Women of Conviction. On this page are several resources, including Women with a Mission: Stories of Early Sister Missionaries, with seven featured stories, and At the Pulpit: 185 Years of Discourses by Latter-day Saint Women, which offers nine discourses by LDS women; there are more in the printed book.
Mormon Pioneer Overland Travel. This database has been cited in several recent BYU Studies articles and books. You can search by a person's name or by traveling company. Notice how many pioneer companies there were in 1847 (we count fifteen). Find links to supporting documents such as a full transcript of the Willie Handcart Company Journal.
Early Mormon Missionaries, 1830-1930. This database can be searched by name, mission, or keyword. The data for this site comes from early missionary registers but is admittedly incomplete; the Church History Library encourages submissions that will correct and expand the data. There are links to documents of each mission and many missionaries, for example Wilford Woodruff's ten missions.
We also appreciate that many items in the Church History Library have been digitized. Kudos to the many workers behind the scenes making things accessible!