Get one of these:
I took my D70 in to have it cleaned once and it cost $75. A friend at work recommended one of these do-dads and it has worked like a charm. Just remove the lens, hold the camera so that the lens mount is facing down, open the shutter and give it a few blasts of air. I was getting the same dust spots that you're experiencing, but not anymore.
I don't know if this means that I'll never again have to have my sensor professionally cleaned, but it should cut down on the number of times I need to do it.
BTW - these should be available at most local camera shops. Or, go here to order it on-line:
http://www.bhphotovideo.com/bnh/cont...ughType=search