The kids thought the Giottos Rocket Air Blower was a toy for them - I suggest you get at least two if you have children around. The Rocket is an inexpensive and indispensable product that should be in every photographer's kit.
Sensor dust is a big problem in the current crop of D-SLRs - especially showing up in macro photography, landscape photography and other photography using a tiny aperture opening or incorporating smooth, light colors such as a blue sky. The Giottos Rocket Air Blower is a key part of my anti-sensor-dust arsenal - and always my first step in cleaning both sensors and lenses.
When cleaning my sensor, I prefer to use air rather than direct contact cleaning methods (which I occasionally resort to). The Rocket uses a hand-squeeze for its very strong burst of air pressure. Air is supposed to enter the blower from the bottom and exit from the top (though not all does) - preventing the dust you are blowing off from re-entering the blower chamber. Rocket fin-like feet prevent the bottom air opening from touching a dirt-carrying surface such as a table top. The fins also keep the blower from rolling away.
The Giottos Rocket Air Blower is very useful for blowing dust from a lens or filter. I recommend using a blower before using contact methods for cleaning a lens. The blower can remove particles that might scratch a lens or filter when wiping it with lens tissue or a lens cloth.
From the pictures I had seen, I expected the Rocket to be a hard plastic device. It is actually quite soft except for the hard plastic tip. Not much hand pressure is necessary to generate a good burst of air.
The large Giottos Rocket Air Blower measures about 7.5" (190.5mm) tall. The medium is 6.6" (168mm) and the small is 5.3" (135mm). My personal preference for general use is the medium size, but the large is very good for big cleaning projects as well. The small is a good travel size - throw one in each of your camera bags.
I highly recommend this product.