As I mentioned in previous posts, I do some molecular dynamics work. It's helpful sometimes to have cartoon-ish pictures to aid in atomic visualization, especially when describing domains with different types of atoms. I'm also a big fan of really pretty graphics, even at the expense of time. I got a copy of Adobe Illustrator CS3 after using CS for way too long, and decided to play around. After a Google search I found out most of the information I needed, but was unfamiliar with the use of some of the tools. After compiling information from a few different sites, I finally got the hang of it. Still, what's the point in learning if you don't share what you know?
Once you're in Illustrator you're going to want to start with a simple circle. I usually show the grid and set snap to grid via the View menu. Make the path invisible and fill the circle with a solid color of your choice. Next, you are going to use the scissors tool (often hidden under the eraser or knife tool) to cut the circle in half. Do this by actively selecting the circle (so the paths are shown, you can do it with the white pointer known as the direct selection tool). Next, with the scissors tool, click the anchor point at the bottom of the circle, and then again at the top of the circle. If this has been done correctly, the middle point of the circle will suddenly shift right as shown in the pictures. Drag the right half of the circle away and delete the left half. Next, select the right half of the circle and go to Effect -> 3D -> Revolve. Leave the settings as the default, and select the preview box. You should now see your 3D sphere. Feel free to play with the lighting and other options, but I've found the default settings look best.