I keep a stash of these in my car now:
Why are clothespins in my car? Well, if you have a young child who likes balloons, they're the perfect "weight" to keep a balloon from flying away. When we're out doing errands, Nate will occasionally be given a balloon at Trader Joe's, etc. Once we're back at the car, I can grab a clothespin from my stash and quickly tie the string to it (I guess if I was SuperMom I'd keep a clothespin in my purse but I'm not, so that's not going to happen). Once we get home, it's fun to play outside with our weighted balloon in the front yard too. It stays just enough above the ground to float around but won't blow away.