Here is a great program for all OS's worth mentioning [i.e. classic and X] but it also works for windows, the program doesn't seem to have a name yet but here it is anyway. It's written by Bryan Tyson.

If you use OS9 or earlier, you could also use a little program I've written, called

Pitrainer Pro 1.2.2

including Picheater 1.0.

And also

Pitrainer Beginner 1.0.1

for those of you who doesn't know THAT many digits...

I wrote these in pascal for MacOS 7 but they work up to 9. If anyone want to make an OS X version of them, please feel free to do so. Just tell me when you're done so that I can get it =)

Here is a pc exe-file made by Oleg Stepanov. It handles the first 1000 digits so far...