I can make decent brushed aluminum. I'll post a short guide and example in a second...
EDIT: Here we go...
1. Create an image, any size.
2. Make a gradiant, any gradiant, beware, it will take time to get a gradient that is good enough. Experiment alot.
3. Create a new layer and set it to the current layer.
4. Goto Filters/Noise/Make noise. Set amount to 10, type to Gaussian, and tick monochrome.
5. Goto Blur/Motion Blur. Set level to 30/35 depending on desired effect.
Here is my example:
Warning, it will take practice with gradients to get decent results, just keep trying.