An alternative to the best Chocolate-Chip Banana Muffins recipe I've ever tried which is here @ http://www.cooks.com/rec/doc/0,194,154179-245203,00.html
You only change 2 ingredients.
1) substitute out the sourcream and use plain yogurt instead (maybe experiment with some flavored yogurts).
2) Increase flour by 1/8 cup (I'm at 3500ft elevation so i increase it by 1/4 cup).

Notes: The yogurt has a much more extreme reaction when the baking soda is mixed in. You'll notice that after the 60 sec. "rise" time you will have a very foamy ingredient. This transfers to the rest of the dough so you don't want to fill the cups more than 3/4 full (believe me).
I didn't change one thing other than what i mentioned here, not even baking time or temp. This recipe is awsome already!
I discovered this when out of sourcream one time and determined to have some of these great muffins. The muffins are super lite and fluffy. The flavor is only a tad liter, but fitting to the liter muffins anyway. I think you'll be pleased.Edit: One other thing not mentioned in the original recipe. Yank them out of the pan and cool on a wire rack imediately. Don't leave them to in the pans for any time at all after they come out of the oven. Big difference.