I usually hate technical/equipment reviews when it comes to photography, but since moving from film Single-Lens-Reflex (SLR) cameras to Digital SLRs several years ago I discovered a common problem that many digital photographers face.
Photographers rarely worried about dust ruining an image back in film days because the frame of film was only exposed to the open air inside the camera for a moment before the film was wound/advanced to the next frame. With Digital SLRs, the image sensor that sits inside the camera is exposed to air (and dust) at all times. This means that dust particles can settle on the image sensor and create ugly dark spots on your images where the light is being blocked by the dust.
A few brave photographers use sensor swabs and sometimes even cleaning fluids to remove dust particles from the image sensor. Most photographers use handheld air blowers to blow dust off the image sensor. Some camera makers have even developed complex anti-dust systems that literally "shake" the image sensor inside the camera to knock dust away. Of course, cameras with this feature usually cost more than cameras without this feature.
The staff at PixInfo.com recently published a review of several cameras equipped with anti-dust systems and made some interesting findings.
Long story short: dust on DSLR sensors is unavoidable without "serious" cleaning using sensor swab-type cleaning tools or slightly less effective air blowers. Anti-dust sensor shake methods don't do anything.