Me? I do all kinds of things: surf the web, listen to music, play games, read e books etc.
I do everything which doesn’t balast my computer.
Jacco;
I sometimes try to get on with some other work that is not too intensive on the computer - editing text/coding. If the computer is running really slowly as a result of the heavy demands I put on it, then I end up going away for a while (sleep, food, dreaded exercise :D, reading newspapers, other things that need doing).
Aligorith
i just watch
I go to sleep!
Under Linux blender is both faster and doesn’t wreak havoc on other programs as much as it does on windows (that is under Linux rendering is faster and I can the rest of the OS is still responsive enough to use). Under windows everything just gets dog slow.
I generally read whatever the latest OSnews, Slashdot or TechDirt article is, then check my email. Rinse, repeat.
Without any further questions: do nothing, it’s natural.
I surf the web, mostly elysiun, or should I say blenderartists, but I’ll sometimes work on my website.
Thats true (I’m running Windows), so I usually surf the web, and this forum. (I’m rendering now, as a matter of fact. :D) Luckily the net is not slowed down since surfing uses virtually no CPU power.
-Laurifer
heh, after taking a shower I am reading this thread…
As soon as I get Blender again, and made stuff that was demanding enough that I’d get bored watching it, probibly pick up my bokken and practice, or go watch TV, or boot up my desktop and use that to render and start another project on this one.
Katsuro
Open Blender on a different computer and work on another project 
When my render is agonisingly slow then I play pinball
But otherwise I surf the net (sometimes elysiun, like now. I’m rendering atm )
Masturbate:D
Nah, I normally just sit there staring at the screen
To speed up rendering and not making windows dog slow, couldn’t you set the processor affinity (if you have HT) for blender?
But anywho, to answer the question, I usually just surf the net, or do some programming.
all of the above
I play music
I surf internet
I draw texure alpas
I use inkscape for SVG goodness
well, I do everything but other openGL or directx applications
If you delete all the fonts , backgrounds, brushes , paterns, gradients, and all the other crap you never use, gimp loads verry fast, and is quite responsive in windows while rendering too!
I have a SMP system, so it only really boggs me down when it is drawing out the image with the threads…
anyways… neat vote thread thingie!!
On the rare chances I actually render something that takes longer than 15 minutes to render (not cause I have a fast computer, just uncomplicated test scenes) I usually load up my Xbox 360 to pass the time. 
reading and writing forums about religious and philosophy, science
make a sandwhich of course, what else!