if you have the kernel source it's in /usr/src/kernel/linux/Documentation/modules.txt, or you can search google for that file. There's also a man page for modules.conf
To get parameters for a particular module on the fly, use modinfo:
~$ modinfo /usr/src/linux-2.4.20/drivers/scsi/scsi_mod.o
filename: /usr/src/linux-2.4.20/drivers/scsi/scsi_mod.o
description: "SCSI core"
author: <none>
license: "GPL"
parm: scsi_logging_level int, description "SCSI logging level; should be zero or nonzero"
parm: scsihosts string
parm: max_scsi_luns int, description "last scsi LUN (should be between 1 and 2^32-1)