Lightly coat a 3 1/2-4 quart slow cooker with nonstick cooking spray. In the prepared slow cooker combine frozen blueberries, frozen raspberries and cranberries set aside.
In a medium bowl combine flour, the 2/3 cup sugar, the baking powder, cinnamon and salt. Stir in milk, melted butter and vanilla just until combined. Spoon and carefully spread batter over berries in slow cooker.
In a small bowl combine the boiling water and the 1/3 cup sugar stir to dissolve sugar. Pour evenly over mixture in slow cooker.
Cover and cook on high heat setting for 2 1/2-3 hours or until a toothpick inserted near center of cake comes out clean. Remove crockery liner from slow cooker if possible or turn off slow cooker. Cool uncovered for 1 hour.
To serve spoon warm pudding cake into dessert dishes. If desired sprinkle each serving with almonds.