As I'm currently writing my diploma thesis in computer sciences and am also working as a programmer, I'm hanging around in front of my computer a lot. Sometimes I feel it's simply too much. Therefore I created two smart lists, one for computer work which can be done now and the other one for tasks which can be done now away from the computer. If I feel my eyes are strained from computer work, I fire up the non-computer smart list and choose a task from there. Both smart lists are based on a "computer" tag which I assign to all tasks to be done at the PC. Here are the (pretty simple) searches for both smart lists:

computer work:
tag: computer AND (due:today OR due:never)

non-computer work (you already guessed it^^):
NOT tag: computer AND (due:today OR due:never)

Have fun with them and cure your eyes with a sweet non-computer task from time to time! :)