What are some dog safe herbs and ingredients?

When baking dog treats, what kinds of herbs or other ingredients can I use to flavor them? I want to be careful of what I use, and not add anything that could harm my dogs. Do you know of anything? Also- is garlic powder dangerous for dogs?

here is just one example:
Cheesy Dog Biscuit Treats
Homemade dog treats are fun to make and healthier than many of the store-bought versions.
I N G R E D I E N T S
1 cup rolled oats (such as Quaker)
1/3 cup margarine
1 cup Boiling water
3/4 cup cornmeal
1 tablespoons sugar
2 teaspoons chicken or beef flavored instant bouillon
1/2 cup milk 1 cup shredded cheddar cheese
1 egg, beaten
2 - 3 cups whole wheat flour.

I N S T R U C T I O N S
Preheat your oven to 325 degrees.
Grease cookie sheets.

In large bowl, combine rolled oats, margarine and boiling water; let stand 10 minutes. Stir in cornmeal, sugar, bouillon, milk, cheese and egg; mix well. Lightly spoon flour into measuring cup; level off. Add flour 1 cup at a time, mixing well after each addition to form a stiff dough.
On floured surface, knead in remaining flour until dough is smooth and no longer sticky, 3 to 4 minutes. Roll or pat out dough to 1/2 inch thickness, cut with bone shaped cookie cutter. Place 1 inch apart on greased cookie sheets. Bake at 325 degrees for 35 to 45 minutes on until golden brown. Cool completely. Store loosely covered. Makes 3 1/2 dozen large dog biscuits or 8 dozen small dog biscuits.

Storing Dog TreatsIn general you should store dog treats the same way you would homemade people cookies. That being said, there are two main variables that determine storage time - the amount and type of fat in the recipe and your local weather conditions. If your recipe uses fats such as butter, or meat bits or juices then it will be more prone to rancidity than a recipe that uses some vegetable oil or shortening. Your treats may mold or spoil much faster in humid or very hot climates.

Here is a recipe that I use:

CHEESE & GARLIC DOG TREATS

1 1/2 c. whole wheat flour

1 1/4 c. grated Cheddar cheese

1/4 lb. corn oil butter

1 clove garlic, crushed

Pinch of salt

Grate the cheese and let stand until it reaches room temperature. Cream the cheese with the softened butter, garlic, salt and flour. Add enough milk to form into a ball. Chill for 1/2 hour. Roll onto floured board. Cut into shapes and bake at 375 degrees for 15 minutes or until slightly brown and firm. Makes 2 to 3 dozen, depending on size.