well, with a recent linux distribution, hotplug is no longer the way to go (on ubuntu 8.10 there are almost no traces of hotplug left over…)
first attempt: udev
the most obvious way seems to be udev which supersedes hotplug…
first, raise udev-verbosity by adjusting its logging level:
sudo udevadm control log_priority=info
find out the vendor- and product-id of your usb-device:
# lsusb
create a rule file for that device, e.g. /etc/udev/rules.d/99-local.rules
# 05e3:0714 -- A-DATA 2GB SD Duo Card
ACTION=="add", SYSFS{idVendor}=="05e3", SYSFS{idProduct}=="0714", RUN+="/script/to/call.sh"
now script specified under “RUN” is called when this very device is connected to the usb…