I understand the LDS Church recognizes the Book of Mormon and the Old and New Testaments as well.
What other works are also considered Scripture? Any Apocryphal works? Doctrines and Covenants?
The LDS Church accepts 4 volumes as "standard works" of scripture:
Each book is esteemed basically equally with the others as pertaining to their scriptural value. Of course, Mormons will emphasize the Book of Mormon since that is the book which mainly sets the LDS religion apart from other Christian faiths.
Several Articles of Faith mention living prophets as God's spokesmen on the earth today, and their importance is reinforced with Biblical teachings by prophets like Amos, Jesus, Paul, and Moses.
Not everything prophets and apostles, seers and revelators, say might be scripture. They are human, and have candid moments as anyone would. So the LDS are careful to distinguish their opinions and other, non-authoritative statements from actual, prophetic teachings over the pulpit in, say, a General Conference.
Teachings of modern prophets are given considerable weight as they have the authority to reveal anew the will of God atop older revelations contained in ancient scriptures.
Not all scripture is general, meaning, intended for everyone. In an abstract sense, any truly-God-inspired words are scripture. But that inspiration may have a narrow scope in some cases, applying to only an individual or a small group of people.
Patriarchal blessings are important instances in a Mormon's life, as these blessings contain their declaration of lineage and also inspired counsel from a patriarch, who can receive such revelation. These blessings become very personal and sacred scripture to individuals. They don't apply to everyone and aren't usually shared.
There have been only two Official Declarations which are published in the Standard Works, but similar declarations, such as The Family and The Living Christ, are equally important. Many Mormons have one or both of these hanging on the walls of their home.
These are likely to contain truth and may be cited reliably, but they are more like secondary sources, in that they draw upon more authoritative scripture from prophets or the standard works to lay their doctrinal foundation, or their main purpose is to edify and uplift, or inform: not necessarily declare doctrine.
These items may have truth in them, but any readings of these should be done carefully with the guidance of the Spirit to discern truth from error.
New doctrine/revelation for the church will never originate from these sources:
It quickly becomes apparent that Mormons believe that God will reveal His truth in a very organized and specific way.
Note that these also may not be affiliated with the LDS Church in any way.
Have I missed anything?
The Journal of Discourses was considered "good as scripture" while they were published. See preface of vol. 3, "WE are privileged to present to the Saints and the world, the Third Volume of the containing the principles of the Gospel of salvation delivered to this generation through the Apostles and Prophets of the Most High, by the power of the Holy Ghost."
Consider: D&C 68:4 4 And whatsoever they shall speak when moved upon by the Holy Ghost shall be scripture, shall be the will of the Lord, shall be the mind of the Lord, shall be the word of the Lord, shall be the voice of the Lord, and the power of God unto salvation.
Any living prophet must find his words in harmony with prophets of God in times past. To suggest that living prophets trump dead ones, does not bode well with the whole idea of "scripture". Is Isaiah to discounted because he is dead? Is Joseph Smith and Brigham Young less prophets now that they are dead? The problem is that these prophets said things under the spirit of prophecy that the modern Church finds uncomfortable. And, wants to distance its self from. These things include prophecy of coming apostacy amoung succeeding leaders of the Church.
Let me suggest that you pray for attendance of the Holy Ghost as you ponder the things that you study, that He may testify of its truthfulness. The same test that you use on the Book of Mormon applies to any other teaching of any other "Prophet".
That said, there are other books deemed authoritative by the Church. These include: "The Teachings of the Prophet Joseph Smith"; "The Articles of Faith", by James Talmadge; his, "Jesus the Christ"; and "Gospel Doctrine" by Joseph F. Smith. On a lower tier of authority, accepted by many LDS, are "Doctrines of Salvation" by Joseph Fielding Smith; and "Mormon Doctrine" by Bruce R. McConkie. (Watch whether you read 1st or 2nd editions, depending on how conservative you are.) "Mormon Doctrine" has been denounced by the Church.