I use Systat and Statistica, both of which run in classic. Unfortunately, neither program has been updated in years for the Mac (new Windows versions are available). I particularly like the way Systat operates except for the klunky data module (fixed in Windows of course), but I don't know if you can even buy it now (SPSS now owns them). A colleague uses JMP as is very happy with it. There is an OS X version for it and a demo, which can be downloaded from here.