These little cupcake cups are a great alternative to buying actual muffin pans. They save space because you can stack them and keep them in a drawer AND you can make different size muffins all in one batch. Plus, they are less expensive than must muffin pans.
Cups also come in silicone and you can buy ones that look like flowers, all of which can be purchased at Bed Bath & Beyond. Another plus side is you don't have to use paper cups when baking and it makes cupcakes a unique shape. The downside to this is it makes for a little extra clean-up and then you don't have a paper to hold the cupcake with when you are serving/eating them. They are creative, convenient, economical space-savers :)