A blender that doesn't puree, froth or whip like it used to may need just one simple repair. Before tossing it in the trash, try sharpening the blades. Carefully disassemble the blender and remove the blade attachment; it should twist right out from the bottom of the blender. Then use a sharpening stone (from any kitchen supply store) and run each edge of the blade along the stone. Make sure you run them on an angle going in the same direction. Repeat for all sides of the blades. Rinse, dry and reassemble. Now enjoy those summer smoothies.