There is often a need with a CSA box to use up the last of the previous box when the new box arrives. Making soup is a great strategy for doing this. Almost any combination of vegetables works well in a soup, and leftover soup stretches the lifetime of the vegetables and can also be frozen with good results.
You can suit the type of soup to the combination of vegetables you have on hand, which is something I like about a CSA: it pushes me to try out new recipes. Okra and tomatoes? Gumbo. Or Indian curry soup. Chard, parsley, and squash? Tortilla soup. Etc.