There is a very nice java package which lets you view crystal structures on any computer platform that supports java (Linux, Mac, etc).
Either cd into the directory and run ./jmol or add the directory to your $PATH environment and run jmol.
I have a feeling I have referred to Jmol in a previous post but I think I’d only used it as an applet then.
The full version alloys export of the images to graphics formats, as well as lots of options that I don’t understand. You can view molecules in 3D if you have the proper pair of glasses, and you can load crystal structures in the xyz format from sites such as Crystal Lattice*Structures at the U.S. naval research laboratory (note this is very different to navel research). I’m particularly impressed by the ability to change the background colour to white, which is particularly useful if you ever want to print something.