Because I'm always forgetting this information when trying to trouble shoot others' systems...

 1. Find the device in the sysfs. For instance, my wireless network card corresponds to
'/sys/devices/pci0000:00/0000:00:0f.0/'.
 2. Examine the 'modalias' file in this directory.
 3. Run /sbin/modprobe -v -n --first-time $(< /sys/devices/pci0000:00/0000:00:0f.0/modalias).
This shows you the module that will be loaded for this hardware.

You can also do this by hand...

 1. Find the device in the output of 'lspci -nn'.
 2. Note the pair of numbers on the end of the line. These are the vendor and device IDs that
uniquely identify the device.
 3. Look this information up in /lib/modules/$yourkernel/modules.pcimap

The same approaches work for USB and presumably all other modern/sensible hardware.