Read a book together. Is there an area of spiritual growth that one or both of you are challenged in? Perhaps God is leading you to missions—there are many interesting biographies and autobiographies written about missionaries. Perhaps God is leading you to trust more fully in Him, whether in general or in a specific area—there are many good books on this as well.
Reading together will help expand your horizons and give opportunities for discussion that you wouldn't otherwise think of. Discuss things you are learning as you read, and apply it to your lives.