Here are my favorite icing recipes. The buttercream recipe is similar to the one posted by upnorthchick but I thought i'd share it any way. Neither recipe is healthy AT ALL, but amazingly delicious.
Buttercream Icing
1/2 cup + 2 Tbsp crisco
4 cups powdered sugar, sifted
1/2 tsp salt
1/8 cup non-dairy coffee creamer (I sometimes leave this out)
1/3 cup water
1 tsp vanilla
2 drops butter flavoring
With mixer on low speed, mix all ingredients together. Continue to beat until mixture is creamy, about 5 minutes. This makes enough to frost a 9 by 12 sheetcake, so you can may need to adjust it depending on the number of cupcakes.
Note: I use this recipe particularly when i'm decorating a cake or cupcake because it holds it shape.
Cream Cheese Icing
This is my favorite icing recipe, especially for cupcakes. It is not overly sweet and very easy which is why I like it.
1 package cream cheese
1 stick butter
1 cup powdered sugar
1 tsp vanilla
Beat first 3 ingredients until creamy. Add vanilla.
Note: You may need to double the recipe depending on the number of cupcakes.
Enjoy!