My idea of making baked goods better for us is not to make them taste worse! I only make changes where flavor is not sacrificed. I use real butter, real eggs, real sweeteners, etc. That's just a personal preference.
Also, the suggestions I'm putting forth won't involve expensive specialty ingredients that require a trip to a specialty store. Not that there's anything wrong with them, it's just that I don't have any personal experience using things like that. I don't leave the house if I can help it, and my weekly grocery trip is all the driving I care to do! And I'm cheap. These are just simple substitutions and adjustments that I often make when making quick breads or muffins.
Typical quick bread and muffin recipes call for the ingredients listed in bold, and my suggestions for substitutes or adjustments or alterations will follow.
White Sugar -- Substitute a smaller amount of brown sugar. Brown sugar has more flavor, so you can use less to get the same sweet impact of regular sugar. You could also just reduce the amount of white sugar you use. (i.e. In my Chocolate Zucchini Bread, the original recipe calls for 2 cups of sugar. I still use white sugar, but I reduced the amount to 1-1/2 cups.)
Eggs -- If the recipe uses two eggs, 1 egg and 1 egg white can be used. If you have applesauce on hand, you can also add in a tablespoon of that. If three eggs are required, 1 egg plus 2 egg whites would work just fine, along with a tablespoon of applesauce.
Vegetable/Canola Oil -- Applesauce again! I typically reduce the amount of oil by at least half, adding in an equal amount of applesauce. Oil really helps keep baked goods moist and tender, and keeps them from sticking, so you don't necessarily want to leave it out altogether.
Sour Cream -- Yogurt, especially Greek yogurt, is a great substitute for sour cream.
I'll continue with more suggestions another day, but I hope this gets you started in making your baked goods a little healthier for you!