Jim Propp asked for essential computer tools for mathematicians. I like the X Screen Saver collection: http://www.jwz.org/xscreensaver/ Probably all Linux systems have this, but it's also available for non-X Mac OS machines. I like it just for the "Ant" screen saver, which does random combinations of number of ants, number of states, number of sides for the cells. It keeps doing things I didn't expect and making me wonder what's next. Some tools are important, but this is an essential timewaster. --Steve