Using the Rounded Rectangle Tool (U), drag out your desired rectangle.
Double click on your layer in your layers palette. The opens the Layer Styles dialog box.
Check the "Gradient Overlay" box.
Adjust the settings appropriately (Choose a subtle gradient for your effect i.e similar shades)
Add a stroke small, but dark stroke (Stroke is the last item in the left menu in the Layer Style menu)
Add a subtle white color dodge inner glow (e.g. size 1 px, full choke, full range, opacity ≤ 15 %)
The shadow is a little bit more complicated as it's not the default drop shadow, or even a common variant of it.
For the shadow follow these steps:
Duplicate the rectangle layer.
Add a drop shadow to the layer. Make it nice and big.
Click OK, closing the Layer Styles box.
Layer -> Layer Style -> Create Layer.
This creates a layer for each layer effect.
Select the "Drop Shadow" layer.
Edit -> Transform -> Warp
Bend the corners down, and push the middle up. This will give you the same effect as the shadow in the picture does. If the shadow is too intense, simply lower the opacity. You may also paint/erase with a soft brush.
Please let me know if anything is unclear or you need me to expand on anything.