Here is a list of some of the excellent resources from the Church on marriage and family relationships:

• Courtship and Marriage: a video interview with Elder and Sister Cook
• Enduring Love video
• Saving Your Marriage video
• Marriage in the Gospel Topics section of LDS.org (Menu > Teachings > Gospel Topics). This topic page has a collection of the best resources on the subject, including lesson ideas and articles.
• The Divine Institution of Marriage on the Public Affairs MormonNewsroom.org
• Eternal Marriage Student Manual. This is an institute manual for the Religion 234-5 course, but it’s also great for  individual and family study. Read text online. Download. Buy a copy. (The teacher manuals for these 2 courses are Building An Eternal Marriage Teacher Manual. Read text online. Download. Buy a copy. and Preparing for an Eternal Marriage Teacher Manual. Download. Buy a copy.)
• The Sunday School course Marriage and Family Relations Participant Manual (Read text online. Download. Buy a copy.) and the Instructor Manual (Read text online. Download. Buy a copy.)
• Together Forever DVD