The finished stock makes a great base liquid for homemade soups.
Save the dirt-free, mold-free, and rot-free scraps, ends, peels, stems from carrots, parsnips, rutabaga, turnips, daikon/radish, lettuce, squash (use the seeds and pulp from these), cabbage, broccoli, cauliflower, leeks, celery, celeriac, winter greens, potatoes, (unless you are avoiding the nightshade family of vegetables), sweet potatoes, apples, onion, garlic, ginger, fennel, parsley, and whatever else you may be using.
Dark red vegetables like red cabbage and beets will create a quite dark-colored broth so you may want to omit these for stock. If using conventionally-grown produce make sure you wash and scrub your veggies extra well. Be aware of strong smelling/tasting cabbage family vegetables and use these for broth when they will not overpower your soup. Store these pieces in your refrigerator in a bag or in a covered container for up to 5 days. When you have a few good handfuls worth of assorted pieces, place them in a large pot with ample amounts of water. Bring to a boil, then turn down to a simmer and cover with the lid just partially open for 20-25 minutes.
Strain through a colander or sieve and use the stock immediately or refrigerate in a glass jar for up to 4 days. In addition, you can save the water left behind from steaming or boiling your vegetables, or from cooking beans and use this as stock.