I found these cooking and baking substitutes on AOL Food. For those of you who are turning your kitchen into a lab and trying new recipes, this might widen your scope of possibilities. Particularly in the chocolate department...:-)
Butter - Use canola oil. (I use olive oil as well.)
Eggs - For each replaced egg, grind a tablespoon of flax seed and dissolve it in 3 tablespoons of water. When it breaks down, it will have the same gooey consistency as an egg, and possess the same binding power.
Or, try 1 heaping tablespoon baking powder, 1 heaping tablespoon oil, plus 1 tablespoon warm water for each egg called for in a recipe.
Milk - Soy, rice and nut milks are good substitutes for milk in recipes. Use the unsweetened kind or adjust the amount of sweetener called for in the recipe. For a buttermilk substitute, use 1 TBSP of fresh lemon juice or apple cider vinegar in non-dairy milk and let sit 15 minutes before using.
Sugar - Use 3/4 C of agave or pure maple syrup for every one cup of sugar.
Flour - Substitute soy, rice or nut flour for white flour in the same amount.
Nuts - Substitute sunflower seeds for higher calorie nuts in recipes because they're lower in calories. Use half the amount of seeds as you would nuts. Or use half the amount of actual nuts called for and toast them to intensify the flavor.
Shortening - Use coconut oil instead of shortening. But skip the kind labeled "virgin" because it has a strong coconut flavor.
Oil - Applesauce is the best baking substitute for vegetable oil as it keeps dough moist and cuts the fat. Use the unsweetened kind and half the amount called for in the recipe.
Chocolate - Use 3 TBSP of unsweetened cocoa powder plus 1 TBSP oil for every ounce of chocolate called for in a recipe.
Buttermilk - "...add one tablespoon of white vinegar or lemon juice to a cup of soymilk... and mix well. It's not quite as robust as buttermilk, but will have a similar flavor." (From vegetarian.about.com)