It's strange...with the Rebel, I never had problems with dust on the sensor. With the 5D, I've had problems with it twice so far. I guess it's time for me to get sensor cleaning gear.
I just set the camera for sensor cleaning, turn it so the opening is facing down, and use an air blower (not compressed air) to blow stuff away. It worked the first time.
Also, for a cheap and readily available air blower, you can get a suction bulb that's used to suck out mucus from babies. Costs about a buck or two and is the same thing as a Giottos Rocket that sells for >$10.