hm, well, I can't say for certain about the hp card reader -- hp seems to me to be pretty forthcoming with their driver information -- Toshiba on the other hand won't release their SD reader info -- so I'm stuck with a nifty looking slot, completely useless without windoze -_-
in any case, try ls /dev/sda*, see what comes up -- then try mounting it
mount -t vfat /dev/sda1 /mnt/sdcard
, where /mnt/sdcard is your mount point (and you'll have to be root)
You may need extra drivers to do this -- and the procedure might even be wrong. The above worked for a USB SD reader, and it's the same procedure as for a USB Mass Storage drive... good luck and I hope it works!