Well, here's Part 2, as promised! I have lots more to share with you, and I hope you find this a helpful reference.
Liquid -- Baked goods usually call for some sort of liquid. This substitution doesn't necessarily save calories, but it certainly boosts flavor: use juice or coffee in place of water/some milk. I use orange juice and apple juice frequently in my baking. Anything chocolate is good with coffee as the liquid! Be creative and use your family's favorites.
All-Purpose Flour -- I substitute about half the flour in a given recipe with whole-wheat flour. It boosts the fiber and vitamins and gives the baked goods a deeper flavor. Going higher than half with the whole wheat may make the texture too dense for your family, so go easy until you learn what everyone likes. P.S. Store your whole wheat flour in the fridge!
Chocolate Chips -- Sometimes, you just can't leave these out, they're so good! But you could reduce the amount used and replace them with diced fruit or even nuts. (Nuts are high in fat, but it's usually the good kind.) Alternately, you could use dark chocolate, since studies have shown it to actually have a few redeeming qualities.
Nuts -- Leave them out altogether or reduce the amount slightly if you're serious about saving a few calories!
Here are some alterations that I frequently employ in my baking:
Use diced fruit such as apples, pears, or bananas to help fill out muffins and breads. Don't overlook shredded or pureed veggies either, like zucchini, pumpkin, butternut squash or carrots. Dried fruits are also a tasty addition, but be careful, as many of them have a high sugar content.
Make your usual muffin recipe using a mini muffin tin instead. Three minis equal one regular-sized muffin, and will help you feel like it's more of a treat. Of course, the danger of that is popping six or eight delicious little bites in one sitting! But even if you eat four or five, it's still less than 2 whole muffins. And all that leads to my next suggestion ...
Freeze half right away to avoid temptation! If you have a big family, they may eat a whole batch in a day or two. But if not, then it may be wise to go ahead and freeze that second loaf of bread or that other dozen muffins for another day.
Spice it up! If your family really likes cinnamon or nutmeg or vanilla or any one of the other flavors in muffins or bread, don't be afraid to use it. Increasing the amount of spice or citrus zest in a recipe will help your family adjust to the denser texture typical of baked goods using whole wheat flour.
Now, go bake some muffins already!