What extra ingredients can you use when baking a bread?

Raisin is the most popular ingredient you can add to a bread. Some bread maker has predefined program to let you drop in raisin after the dough is knead. Some other popular options include chopped walnut, and cinnamon. In general, you can't go wrong with nuts because they give a nice twist to the flavor.
If you want to be creative or exotic, you can also try cheese or beer, but not everyone likes the strong flavor.