The mirror flip up & sensor mechanism are sensitive things, and like spheredom has highlighted, good sense prevails (eg. sticking the vacuum tube right above the sensor is NO NO NO!)
I do it on certain intervals, on a 1800watters household vacuum cleaner, specifically on a Nikon d90. It has kept my sensor, lenses etc spick and span.

I have read someone getting into trouble with the vacuum cleaner. So if anyone needs detailed steps on meaning of good sense prevails, then this is not for you. (I dont wanna post the steps for I may sabo you instead!) It really aint too pricey to have it done at NSC.