I've been trying to get various things to work on my laptop, one of which is a synaptics touchpad, and I have made about 5 kernels so far. Is there any way in which I can just create a module for the device I want, without recompiling everything? If I have the module compiled into the kernel, and want just the module, will I need to compile the kernel image again?

If the module is compiled in the kernel you just issue

You can run something like "make drivers/usr/serial" to build te files in the drivers/usb/serial directory, or
"make drivers/usb/serial/visor.ko" to build only the visor.ko module.

Note: from Linux Kernel in a Nutshell, page 27

Each of the two previous responses to this thread represent two slightly-different interpretations of your problem... and both of them, it would seem, are slightly-different from yours!

(1) You seem to be concerned that the module has not been compiled. make modules should take care of that... "jschiwal" seems to address that interpretation in a slightly-different way...

(2) Bruce points out that the modprobe command may be necessary to ensure that the module has actually been loaded into the kernel...

To completely rebuild a module in a kernel downloaded from kernel.org follow these steps.

1. Go into the top level directory of your compiled kernel source tree. It MUST be the one you're booted from.
2. Type "make M=subdir" where subdir is the directory that contains your driver.
3. Find your module - it will be xxx.ko and in the sub directory your compiled.
4. "rmmod xxx" where xxx is your module
5. "insmod xxx.ko" where xxx.ko is the path to your new module
6. Test it.

Note that you cannot use this method for the disk device for any mounted drive; most especially your root drive. If this is what you want, you will need a spare working kernel to fall back on, because your only option is to replace the xxx.ko file in /lib/modules/whatever and reboot.