I might as well try to answer your question since it seems to be a rule now. I don't want to try and think about all this ground stuff, so I'll just tell you what I do, and if it's wrong I have a feeling someone will tell me.

If I'm getting in the case, I turn the case power switch off and the UPS switch off. I leave it plugged it. Like Scott, I've developed the habit of constantly touching the power supply to discharge any static that may have built up on/in my body.

If I have to unplug it, I use a wrist strap. I get a length of zip cord and clamp the alligator to one end and attach the other end to a wall socket screw. Now I'm discharging any buildup static to the same ground as before, just a different path. Forget about all this ground stuff - if the box is plugged in and you touch the power supply, it's the same thing as touching that screw on the wall socket, but the wrist strap just makes it more convenient, so you're sort of always touching it. The point is to give it somewhere to go other than the mobo.