I have made cake balls a few times and have always been pleased with the results. I have always used my own cake and homemade frosting so I know the ingredients are top quality. My best are the ones that come from Martha Stewart's One Bowl Chocolate Cake recipe and Fry's Fudgy Icing (recipe below). The combination does not disappoint, especially once dipped in good semi-sweet chocolate and shared with a friend.
After you dip these, you can sprinkle things over them right away before they set if you like (sprinkles, nuts, coconut).
So, here's how it goes. Bake a cake, cool. Make a batch of frosting. (If you make one 9" cake, make enough frosting that would just cover it, I'm guessing 1 cup or so.) Crumble your cake in a big bowl into crumbs, seriously, break it up. Even if it has a nice crusty edge on it, break it up nice and small, forget the crust, what you're going to make is so much better anyhow. Dump your prepared frosting on top and mush it all up. I've started with a pastry cutter and then moved to my very clean hands to completly incorporate it. It should be mushy. Put it in the fridge for about an hour to chill and harden. Take a heaping tablespoon of the cake / frosting mush and roll into a nice ball. Repeat until all your mush is gone (eat as much as you want as you go, of course). Chill again while you gently melt your chocolate. Roll each ball in the chocolate and let chill again. Serve, eat, devour, or freeze for later (they do freeze well). This can be done with scraps and leftovers as well, throw them in a bag in the freezer and when you get enough cake bits, make some cake balls.
You can use any combination of cake and icing flavours to suit you, here are some suggestions. If you want, you can stick a lollipop stick in each one before you dip them, then you have cake pops, fun too!
Fry's Fudgy Icing
from my mother's Fry's cookbook and in my repetoire since 1997
3 Tbsp butter
1/4 cup cocoa
1/2 tsp vanilla
2 cups icing sugar
1/4 cup milk
-mix butter and cocoa well, add vanilla. Alternate adding the icing sugar and milk to desired consistency.