Justin Taylor has a written a number of short articles on Martin Luther and marriage over at The Resurgence:

• Luther: The 40-Year-Old Virgin?
• When Martin Met Katie
• The Original Lutheran Marriage: Love and Marriage Aren’t Always Like a Horse and Carriage
• The Luthers’ Marriage
• 4 Lessons from Luther on Married Life

For more on Luther and his marriage, see Taylor’s chapter “Martin Luther’s Reform of Marriage” in Sex and the Supremacy of Christ, edited by John Piper and Justin Taylor available at Amazon and WTSBooks.

You can also get a free PDF of the whole book online from Desiring God and more resources from the 2004 National Conference: Sex and the Supremacy of Christ.