Put the single people together at a table, so they have someone to talk to.
My HMO doesn't cover the number of therapy visits it would take to mitigate the trauma I'd experience from this.
Admittedly, I'm a reclusive misanthropic freak, so I'm not the best person to have at a social event like a wedding reception anyway.
My only sane post-college roommate was a girl who I met when I -- in a TOTAL departure from my misanthropic ways -- joined a volleyball team all by myself. I didn't know a soul on the team, and while it was mostly awkward, sometimes it was fun, and I got along really well with Molly. When I mentioned that my insane roommate was moving out and I was going nuts trying to find an affordable 1-bedroom in a not-scary part of town, Molly said that she was about to look for a new place, too.
And while it could have been all Single White Female, she was actually the best roommate I ever had. But even though we had parties at least once a month, I never became actual *friends* with her friends; although the parties were fun, it was clear that they were Molly's friends and just my acquaintances.
When Molly got married, she invited me to the wedding (with a +1), and I had NO ONE to take with me. So I went by myself, and endured one of the more excruciatingly painful evenings of my life. And when I tried to leave the reception after waiting 45 minutes or so after dinner and cake were over, instead of letting me gracefully slink out the door, Molly kept making a big deal out of it: WHY did I have to go NOW??? Didn't I want to stay and DANCE????
(Yes, she's the bride, and it was her special day, so I was tolerant of her attempts to get me to stay, but I held fast and booked it out of there before the dancing started. I think it was when she said "Oh, but [names of her other single friends who I knew tangentially] will dance with you!!! It'll be FUN!!!!" and those aforementioned tangental friends looked at me with dead-eyed panic that I knew I had to leave, even if it involved breaking one of my own limbs in order to get hauled off to the hospital -- anything to get out of there before the goddamned Electric Slide started.)
(Seriously, y'all, I am SO MUCH FUN.)