Rather than just offer a one time congratulations, make your wedding wishes last all year long. Each month in their first year of marriage, send the new couple a special gift and a small note. The note might say something like "Don't forget to count the smaller milestones in your life together."
The monthly gifts can be based on the couple's hobbies, seasons, or another theme. For example, send a package of gourmet hot chocolate in January or a gift certificate to a favorite ice cream parlour in July. Your thoughts will be with the new couple all year long, and might just give them a great reason to spend time together and stay connected once the honeymoon period is over.