This might sound very silly but you just never know.....
I was cleaning my sensor (on a 30D) with a rocket blower and when finished I forgot to turn off the camera as the manual recommends. I proceeded to attach my lens with the sensor still in the 'clean' position. I quickly realised and tuned the camera off, thus flipping the sensor back to its normal position. Although I can't see this having any detrimental effect (apart from further dust with the sensor being exposed - after the incident I repeated the whole cleaning process to make certain) I'm not entirely sure. Can this cause any physical damage to the camera?
[Edited 2007-03-04 16:05:52]