I was very excited to stumble across PSPP this afternoon. I've had a little play and come up with a simple Perl module that wraps the pspp binary and scratches my itch of wanting to generate downloadable SPSS-compatible files (.sav) on the fly from a website.
It's nothing more than a dumb wrapper at this stage, but please let me know if you're interested in using the module from your own Perl code and if so what sort of features/API might be desirable.