iPAQ development

Anyone ever done some development with an Compaq (or HP now) iPaq?

I was looking at making a PCMCIA based interface so i can use the fast CPU in it for simple data analysis tasks. As such a faster than serial (USB/rs232) interface is needed.

Anyone know any sites or have tried this themselfs, the hp developer stuff seams very out of date. I want to only use a low end micro for the interface too, PIC16 series or low end AVR.

just to clarify i mean PCMCIA by an expansion jacket i have spare thats slightly broken, if straight in of SD would be easyer than it will be SD.

But surely someone has tried this, or can give me some good links to start with?