A surfeit of spotty bananas on the counter and some getting-on blueberries in the fridge yesterday led me to this Martha Stewart recipe for Healthy Banana Blueberry Muffins, which I wanted to recommend.
I have an aversion to whole wheat pastry flour, but I used it here because it was all I had in the house (bought for another project) and I substituted it for about 1/4 cup of the white flour too, since I was out. The result was a lovely fine crumb that still tasted pleasantly wheaty, without that sour whole wheat pastry flour aftertaste. I also added the zest of one lemon, which I would highly recommend. Next time I'll try just plain whole wheat flour (it would give the muffins a bit more body), use the whole wheat pastry flour instead of any white, and halve the sugar: it calls for 1/3 cup of both white and brown, but I'd just stick with the brown. Martha's recipes tend to be pretty sweet. I think you could also substitute apple sauce for some of the butter if you had to, and maybe try raspberries. The recipe calls for frozen berries, which tend to hold their shape better, but fresh ones worked pretty well. The muffins are still being enjoyed by the entire household. Again, the recipe is here.