Powdered sugar just isn't something that I keep on hand, but regular sugar is! In addition to the fact that I don't really use it that often, I don't keep powdered sugar on hand because I don't trust it. If you are vegan or vegetarian, you may like to know that some sugars are filtered through bone char as part of the bleaching process. Additionally, powered sugar can have corn starch or tapioca starch added, which is fine, I guess, but not necessary to me. When I make powdered sugar, I like to used turbinado sugar or other unrefined or unbleached sugars (which is what I have in the house anyway). As a sugar in general I think that raw has a more complex flavor and well...it just tastes better to me.
To make powdered sugar, all you need to do is is toss some (at lease 1/4 c.) in a blender, or my personal favorite, a magic bullet. Blend on high stopping every 15 seconds or so to give the sugar a shake, mixing it up. Process until very fine and powdery. Tah-Dah! Super easy.