For the sweet side of cooking, there is another list. It's harder to push you to make desserts without recipes, since, in the case of baking, you can't really off-road it. So this list applies to making desserts both with, and without recipes.
Here is a list of pantry staples that having on hand at all times will make it easier to make dessert. If you haven't made many desserts, you should start out by studying some cookbooks. Desserts, especially baking, are harder to make using some inspiration and instinct alone. Take it with a grain of salt (or sugar), and leave suggestions for pantry basics I've left out that you feel are essential for the way you like to make dessert.
- Sugar. Obviously.
- Brown Sugar. Granulated sugar + molasses = brown sugar. It has a softer texture than granulated sugar. Light and dark brown sugar differ only in their percentage of molasses. When in doubt, use the lighter variety.
- Confectioners' Sugar. aka Powdered Sugar, is finely ground granulated sugar with a touch of cornstarch, which prevents it from clumping. It's used to make icings and is nice to dust atop an otherwise plain looking dessert.
- Honey. A nice alternative to sugar that lends an earthier flavor, especially nice with oats and nuts.
- Unbleached All-Purpose Flour. Pretty much any baking starts here. If you plan on making anything with yeast, you will want to try some bread flour as well.
- Pure Vanilla Extract. The imitation stuff is a different beast. Keep a bottle of pure vanilla extract on hand for cakes and cooking, and to enhance icings, ice cream, just about anything sweet.
- Cinnamon. Aside from where it's called for in recipes, cinnamon is great for sprinkling on about-to-be baked fruits like apples and pears.
- Nutmeg. Better to grind it fresh yourself. Your whole kitchen will smell great and the taste is superior.
- Baking Powder and Baking Soda. For baking, these are essential. See Pantry Basics: What's the Difference Between Baking Soda and Baking Powder for details.
- Fine Granulated Salt. The kind you can pour. Skip the iodine if you can.
- Cocoa Powder. Unsweetened chocolate - cocoa butter = cocoa powder. Dutch-processed cocoa is richer and darker than unsweetened cocoa and are not necessarily interchangeable.
- Chocolate. These days there are dozens of varieties of chocolate available. Semisweet and bittersweet are the two varieties most often called for. There is a vast difference in flavor between lower-end and higher end chocolate. If you can afford it, try easy-to-find brands like Scharffen Berger, Callebaut, and Valrhona.
- Nuts. Walnuts are the most commonly called for nut in desserts, but peanuts, hazelnuts, almonds, macadamia nuts and cashews also have their day in the sun. If you're going to keep one on-hand, it's walnuts.
- Oats. With a sack of rolled oats at your disposal, you can make oatmeal cookies and struesel toppings for fruit crumbles. You can't go wrong with either of those desserts.