I wrote vows for my ceremony. (Such a great "exercise" to reflect on our marriage. Man, I cried. 
) But before that of course I looked online for ideas. I thought these were good sample vows for renewals. Or at least a good start.
Renewing Your Wedding Vows for an Anniversary
(spouse's name), __ years ago, I pledged my love and commitment to you, but it seems like only yesterday. I promised to love you, honor you, comfort and keep you. I pledged to be by your side in sickness and in health, in times of want, and times of plenty, for better or worse, for the rest of our lives. We have had all of those things, and you have been by my side as we created a family, a home, and a life together. Today, at the beginning of our __ year as husband and wife, in the presence of God, and our family and friends, I renew my vows to you, pledging my eternal love for you, and eagerly awaiting what life may bring us.
Vow Renewal After a Private Wedding
With great joy I pledged my love and commitment to you on our wedding day. But a loving relationship does not exist in a vacuum. Our family and friends first showed us how to love, helped us grow, and supported us when we found each other. I hope they will continue to love and support us as we love and support them. Therefore, I am delighted today, in the presence of these witnesses, to reaffirm my commitment to you, and once again, to promise to love you, honor you, and comfort you, in sickness and in health, for richer, for poorer, for better and for worse, as long as we both shall live.
(I personally might take out one of the lines about family and friends or re-word it a bit but I like the idea of acknowledging them as they are the essential reason behind the second ceremony.)