A glass orb can be used for many graphics, interfaces, and website layouts. It is also very easy to make. Here is the way I make my glass orbs in Paint Shop Pro 9.

Make a new layer Layers > New Raster Layer. With the "Selection Tool" set the "Selection Type" to "Ellipse". Make a small elliptical selection near the top of your circle. Then Selection > Modify > Feather Set the number of pixels to 30. Choose the "Fading-White" gradient and flood fill the elliptical selection.