I love "small world" moments. Perhaps because my family moved frequently when I was growing up, but anything that makes me feel connected to a larger whole warms my heart.
Recently I was walking to my work (I live six minutes from my office--seven if there is traffic on the one street that I have to cross), and I started chatting with a guy who just moved in a block away (actually we don't have blocks, we have trees, so I should say moved in a few acres of trees away). Well, it turns out that not only was he from Fresno, California, where I lived for awhile growing up, but we attended the same church at the same time. Cool.
Another: At a party in Fresno I met a guy who went to my high school whose daughter attended the same small elementary school out here in Storrs, CT as did my son.
My favorite: A used-book buyer came to my office one afternoon, and we started chatting. I learned that he grew up in Bozeman, Montana, where my parents were from, and his doctor was my (revered) grandfather! He pointed to his leg and said that when he broke it as a kid my grandfather put it back into place. I had a hard time working the rest of the afternoon I was so teary.