There is apparently new standard, called Express Card, which is a miniaturized implementation of the PCI Express standard, which has been used in expanding the desktops for a while.
The funny thing is that laptop manufacturers have started putting these Express Card slots instead of the PCMCIA ones, but AFAIK there are no express cards available yet.
I am sure that with time there will be a wealth of the Express cards manufactured, but for now you have to stick with the USB/Firewire.
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Regards,
Alex