I don't have one, but two sets of incredible in-laws, due to remarriages.
My husband's mom has treated me like a daughter since the beginning. She is a great friend and I can always be honest and open with her. Over the past 20 years, we have shared a lot of laughs, and a few tears. We talk on the phone all the time and we see each other when we are able to make the 5 hour trip. She goes out of her way on holidays to wrap way too many adorable gifts. Even though we're in our 40s, we feel like her 'kids' and she always is there for us emotionally.
I knew she was a gem, but what grabbed my heart the most was when she made a special trip to town just for me! It was when I had surgery and would be down for a few weeks, she just said she'd be coming to help. It turns out I didn't need much help at all, but I will never forget how I was 'one of hers' and how she was, and is really here for me as much as her own two children. We absolutely love to 'go see Mom'.
My other mother-in-law, my husband's step-mom, has also been a great joy. She and my husband's dad are super fun in-laws and keep the family together. We enjoy their company immensely, and they are way funnier than we are. They have taken us to places we never would have gone, and helped build lifelong memories we will have forever. They create special holidays and 'just because' get-togethers. They take interest in our lives and never are intrusive, yet we always know they are there for us.
What a lucky girl I am to have been blessed by such wonderful, strong, lovely women! I hope this can inspire other in-laws to have incredible relationships with their daughter-in-laws that love their sons so much.