I had a hole saw that fits onto my rockwell sonicrafter. http://www.sonicrafter.com/ There are cheaper ones on the market.
"What is the Rockwell SoniCrafter?
The Rockwell SoniCrafter is a small, hand held multiple purpose tool. The SoniCrafter features Microsonic™ technology,
which creates a high frequency oscillation motion. The tool is adapted for a wide variety of applications by attaching
specially designed accessories on the end of the oscillating shaft. The SoniCrafter by Rockwell Tools is excellent for sawing, sanding,
scraping, cutting, rasping and removing grout."
I will post a picture once I can get access to a camera I am snowed in by storm of Feb. 6 2010
I had more than one type of hole saw and the other I tried doesn't fit and the other oscillating tools probably have different ends too
so shop around to find the right fit.
It makes the job much easier.
Hope this helps.