A great idea for leftover yarn is to crochet a dog bed. All you need is two circles, big enough for your dog, sew them together and then stuff them with stuffing, or an old pillow, or old clothing you were thinking of donating.
If you don’t know how to crochet a flat circle, this lady will teach you.
And then you just make your bed whatever size you want. Count your rows and make a second circle the same size.
They don’t have to match, in fact, it’s fun if they don’t, then you can flip it over depending on the colors or look you want. Maybe one side fall colors and the other side spring colors.