I have about 50 cookbooks and many, many food magazines. I don't use them all, but I'm loathe to part with any. I never know when inspiration will strike and I'll pull one off the shelf. I have cooked from most of them or used them as reference to learn about particular ingredients or cooking methods.
Recipes clipped from magazines and newspapers and printed off the computer go into multiple pocket file folders from an office supply store. I have 3. One holds main dishes (seafood, chicken, pork, lamb, beef, pasta, vegetarian). One holds lighter fare (beverages, appetizers, egg dishes, salads, soups, perserves). One holds baked goods (cookies, muffins and quick breads, yeast breads, fruit-based desserts, pies and tarts, cakes).
When I travel, I try to find a good local cookbook as a souvenir.