a 1GB microsd card in a micro-to-normal sd adapter in a 6-in-1 pcmcia adapter from sandisk. put that into the mac. interestingly, the mac can see the card, can tell what kind of fs is on it, etc, but won't mount it.
Put it in the HP, it can't cope. can't read the card, can't format the card.
Put a 16mb CF flash card into a cf-to-pcmcia adapter from viking. put that into the mac, it sees and mounts the disk just fine.
Put it into the HP, and again, no read, no format.
Supposedly, people are out there using flash cards with the HP, but I ain't feeling the love. I don't have any actually-pcmcia flash cards laying around, only cf or smaller, so I can't test with that.
I'm actually pondering something stupid, like getting the phone or something to talk SIR to it and transferring the files there, then bluetoothing them over.
edit: Tried it with the zaurus, but I don't have a plain serial comm app on it, so I'd need to find one.