If for some reason you need to create many reflections or you have to create a few of them but constantly, you might want to speed up this process a little. For example, this website has a reflected icon for each photoshop tutorial ant they can be created pretty easy with a little bit of automation. Too bad the method i'm about to describe only works on fixed-height images. The width shouldn't matter. So here's what we are going to do:
In this case i had a background (gradient) and i wanted to create a few icons on it. Here's how it works. Let's say you also have the same background with some width that we don't really care about and height of 80 pixels. And you need to add 50x50 icons with reflections. Each icon will be created in a new document and then pasted and placed on the original. So since our icons will be 50x50, we will need a new document with dimensions of 50x80 pixels. So go ahead and create a new document with these dimensions. Now take the gradient tool

from the
tool palette and set the colors to: foreground: black, background: #333333. Draw the gradient from top to bottom, holding the
SHIFT key on your keyboard to keep it straight. You should get something like this:
Now take some icon you need to reflect and paste it on the background. Note that before pasting you should create a new layer (though photoshop should do this automatically) by pressing the new layer button

in layers panel. After pasting the icon, position in the top of the background. You should get something like this:
Here's the icon, if you want to use it too:
Now select the background layer and pres
CTRL+J. This duplicates the background layer. Select the duplicated layer and place it above the icon layer. Finally, you should get something like this:
You will probably notice, that the icon has now disappeared. That's ok, we'll fix this later. For now, make the top layer invisible, by clicking on the eye next to its icon. You might want to make the original background layer as well. Then select the icon layer and let's start the fun part. If you don't see
actions panel, click
Window > Actions in main menu to bring it up. What we are going to do is write a new macro to create a reflection from the image we have. Press the create new action button

in actions panel. Enter some description for it and press
Record. Now whatever we do, photoshop can replicate automatically later on. So first we duplicate our icons layer. But do not duplicate it with
CTRL+J this time. Instead, click on the layer and drag it on the new layer button

in layers panel. Now select the duplicated layer and press
Edit > Transform > Flip Vertical in main menu. Press the
on your keyboard to move the duplicated layer and move it down with the down key until it is placed below the icon. What happened here is that a part of image is now out of bounds and is not visible. I personally did that on purpose, because i don't want to apply the reflection on the whole icon - it would be too big. So by applying the reflection on a smaller portion of the image, reflection itself gets smaller. You can now stop recording the macro by pressing the stop button

in the actions panel. That's done, the action is now recorded. But we didn't get any reflection? That's right, we didn't. The reflection itself won't be automated. It will be prepared only once. To do so, move the original icon layer above the duplicated background layer like so:
You can now make the duplicated background visible again, by toggling the eye next to it. After doing so, only the upper icon should remain visible. Select the duplicated background layer and press thelayer mask button

in layers panel to make a layer mask. Now select a part of image that is below the original icon like this:
With the masked layer still selected, take the gradient tool (it should have changed to black and white gradient by now) and make sure the foreground is black and background is white. Draw the gradient on the selected area from top to bottom, by holding the
SHIFT button again to make it straight. You can draw all the way down or you could leave some space at the bottom. Deselect the image (
CTRL+D). If you left some space at the bottom, you should get the result similar to this one:
No two more things left to do: select the portion ot the image, where the original icon is located, then select the masked background layer and fill it with black color (
ALT+BACKSPACE):
Then place the icon layer below the masked background. If you did everything ok then nothing should change and you should still see an icon with a reflection. And the layers panel should now look like this:
So here we go, we have an icon with the reflection. So how exactly the automation will work from now on? Simple. Delete the duplicated icon layer, then save this file somewhere on your computer, because from now on it will be a template in creating the icons. Also you might want to select the original icon layer and hit
CTRL+A and
DEL to clear all of its contents before saving. Whenever you need to create an icon with a reflection now, just open this template document, place some icon on the icon layer in the top of the image, having the icon layer selected, choose the recorded action from actions panel and hit the play action button

. A new layer will be created, the icon will be duplicated, flipped and moved down. And since we have a masked background on top of it - it automatically adds the reflection. Now simply hit the
CTRL+A and
CTRL+SHIFT+C to select all the image and copy all the layers. Paste it whereever you need it.