Here is a quick and easy way to make objects appear as if their made of glass in Photoshop.

1. Start off by opening an image you would like to turn into glass.

I have blue squares in the background to help show the transparency of our object better, so don't worry about those.

2. Now we'll begin the process of turning your image into glass. Begin by selecting the layer which your object is located on, then proceed to Blending options by clicking

Layer --> Layer Styles --> Blending Options

Set Fill opacity to 0%.

Now move onto Bevel & Emboss, apply the setting as you see them in the image to your left.

3. We now need to add some highlights and a drop shadow to your image to make it appear as if it was real glass. To do this, while still in the blending options, apply the settings shown to your left in the Drop Shadow & Inner Shadow tab.

4. Now that you have applied all the settings you should have something similar to the image shown to your left. With a little creativity who knows what you might be able to accomplish with this effect.