Saving seed from crops is a money-saving way to preserve favorite varieties and share with others. The document outlines how to save seed from various crops, including easier crops like lettuce, peas, and tomatoes, as well as trickier crops like onions, radishes, and brassicas. Proper seed saving requires planning space and isolating different varieties to maintain purity and prevent cross-pollination. With the right techniques, seeds can typically be stored and used for growing for several years.