The following document features designs for the Dirty Kitchen Cooking Timer app available for iOS, Android, and the Blackberry Playbook.
These designs were created in Photoshop, but could easily be done in Flash or Illustrator.
As you can see, simple flat geometric shapes can appear entirely 3D by adding simple Bevel and Drop Shadow effects.
For metallic surfaces, gradients can help add depth and shine.
Note: use knockout under the blending options for each of the three inner layers so they will cut through any bottom layers.
Note: I added a bitmap photo of a kitchen and set its opacity very low so that it would appear to be a reflection.