A can of compressed air works for me.
The way I do it (others may do it differently) is to slightly squeeze the trigger on the can of air so it will not blow at full blast, so it might be about the same power like the regular rocket blower (but I like it a little bit stronger).
And when you spray the air into the camera, make sure that the straw does not go into the body portion of the camera. Keep a good amount of distance from the tip of the straw and the sensor.
The problem with canned air is that you have to take care. One brand/type of canned air will be safer than the other. Some cans will spay propellant if you hold them the wrong way. Spraying the liquified gas onto the sensor is a bad idea. Also, some canned air contains traces of lubricating oil. Again, not a good idea. My Canon 10D manual explicitly states I should not use canned air.
So, it's just like me using qtips. It's no problem at all if you take care (have high quality products and use them properly) but you can get into problems if you do not.
