You guys missed a big one.
Shop where there is no sales tax.
For example, you can purchase by phone or online from B&H Electronics (not affiliated in anyway) and if you don't live in NY, you don't pay tax. I saved a bunch of money by doing this when I bought my Powerbook several years back.
Whatever discount Apple gives on Black Friday is not likely to be as good as avoiding tax... at least if you are making a $2k+ purchase (I could be wrong).
5 Tips For Getting The Best Deal on Apple Purchases