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.

Now select your "Selection Tool" set the "Selection Type" to "Circle". Also make sure "Anti-alias" is checked. Make a circle selection just smaller than the canvas size. Set your foreground color to "000000" and your background color to "404040". Now choose the "Foreground-Background" gradient and flood fill the circle selection.