There is softwarre from a company called Aerize that supposedly allows running of apps from an SD card. Here's
the link to the company's websites entry for that app. I haven't tried it, I'm not willing to pay $20 for it just yet. It would be nice if RIM actually would enable this function in their next major OS upgrade. To me, this is one of the fundamental flaws of the Blackberry. Except for the StevePhone, every other smartphone out there allows running of apps off the memory card, and I'm guessing that RIM with its obsession about security is using that rational in not enabling this function.