This is perhaps the most recent activity from my relationship. To encourage our reading of good Christian literature, we have agree to get each other two books of each ones choice, which the other must read, a year. If reading isn't your thing, two books a year is really manageable.
One good idea is to have a prayer calendar for the month or week that you both follow so that everyday, you pray for the same things and people. You can also share prayer requests every week or day or month.
Careful, this one may expose your inconsistency in personal devotions. Its a good way of keeping each other consistent in devotions. If your mate is always sending you devotions, you soon feel challenged that you haven't been sending yours.
It is lovely to work together in the same ministry with your mate. Its a great way to be together and yet work for the Lord. Your prayers for your endeavors for God are then similar. You share the same heart and burdens for your spheres of ministry etc. I recall listening to a sermon where a pastor spoke of a couple his former church. The lady was exceptional at teaching children but stopped to join her husband in his area of the media ministry where they served together in the church faithfully. Whatever you think of the lady's decision, I'm sure it added a certain dimension to their relationship that you don't find in couples who don't serve together in the same ministries.
Sharing Sunday Lesson
Another good one is sharing what you learn from the preaching of God's word in church every week.
If coming up with these things seems difficult, you can approach older couples, married or otherwise and hear what activities they engaged in together.