The below is bit old article, but it explains the internals of module loading and unloading well.
http://www.tldp.org/LDP/tlk/modules/modules.html
This is the the similar article, but it is based on kernel 2.6.
http://download.boulder.ibm.com/ibmdl/pub/software/dw/linux/l-lkm/l-lkm-pdf.pdf
The below is the list of module tools.
module tools
insmod
rmmod
modprobe - this is wrapper of 'insmod' and 'rmmod'
depmod - create module dpendency
modinfo - display module info