Some dust spots on the sensor will absolutely not shift with air-pressure (blowing) alone. To shift them you need to wet clean the sensor.

I was nervous the first time I did this as I can understand most people would be. But it is not that difficult or risky, basically it involves wiping the sensor assembly with a soft rubber "wand" with a cleaning fluid dampened wipe attached to it. At this point it's worth stressing:

You are not cleaning the sensor microchip itself you are cleaning a toughened piece of glass (the low pass filter) that sits on top of the sensor.

The only damage you can do (when using the correct fluid) would be to the delicate shutter curtains, so make sure the shutter is open and will remain open for long enough to clean the sensor. This usually means ensuring the camera's power source remains uninterrupted.

Eclipse fluid has been tested on all sensors and determined to be safe. It's basically just alcohol and will evaporate without residue. See:

http://www.photosol.com/guarantee.html

Likewise PEC PADs are highly recommended to go with it. I suggest you get a kit that includes the basic rubber wand, fluid and pec pads, then replace the fluid and pads as they run out. This is a very cost effective solution compared to all in one wet cleaning solutions. All you have to do is wrap the pads round the wand and tape them each time.