Here's one my mom always made when we were up to our eyeballs in zucchini:

Chocolate Zucchini Cake

2 1/2 c. flour
1/2 c. cocoa
2 1/2 tsp. baking powder
1 1/2 tsp. baking soda
1 tsp. salt
1 tsp. cinnamon
3/4 c. margarine, softened
2 c. sugar
3 eggs
2 tsp. vanilla
2 c. shredded zucchini
1/2 c. milk
1 c. chopped walnuts

Mix together in bowl. Bake in greased, floured cake pans until toothpick inserted in center comes out clean (careful not to over bake; start checking at 25 minutes or so).