We use Moosewood's "Muffin Madness" recipe. Our favorite is the banana muffins--we double the chocolate chips, but you could also use none to make them more healthy. The same recipe can be used for full-sized or mini-muffins, just adjust the baking time. (We bake full-sized muffins 25 minutes, mini for 15.)
The recipe is copied on this webpage--use the base recipe with one of the variations, as they're not meant to be eaten as the base recipe alone:
http://www.recipesforlaughter.com/2009/06/moosewood-muffin-madness.html