Here's our trick which worked for us to get our Wii and our Wii Fit. My friend did the same last week and was able to score both also.
We called around to a few places and found that Gamestop was the most friendly and helpful. We also learned that they get their shipments on either Tuesday or Wednesday each week.
We called our local Gamestop on Tuesday around midday and they had some, but could only offer to hold them for about an hour. Since I was at work with the $$, we had to wait. Hubby called again at 5:30, just as I was getting off the train, and they still had some. So I headed right over and picked it up. With the Wii Fit, we got it on the Wednesday after Labor Day. Followed almost the same procedure, except that I made sure hubby had the $ so he could pick it up on his lunch hour.
None of the other stores were really willing to give us an idea of when they might have them. Target's response: we get stuff every night, so just call every morning to check. Circuit City would get shipments on Saturday afternoon, but would never tell us if there were any Wii's in the order. They just told us to show up every Sunday morning when they opened to find out if they had any.