The source (not source code) of /lib/modules/2.6.24-*/ubuntu

     Just a web search on 'acer_acpi' provides links to look at; I'm pretty sure they're both drivers for your hardware, but you could search them out on-line and find out more about them.

Something like this?
http://www.mjmwired.net/kernel/Documentation

http://www.mjmwired.net/resources/mjm-kernel-docs.html

To Larry Jordan: It's easy to find out that acer_acpi is housed in http://code.google.com/p/aceracpi/ and the detailed documentation about it is available on the site, but it is not the case for intel-agp-ich9m; I have googled for it in vain. So, this is not the answer that I am looking for.

To Sam: Those are the documentations of the mainline kernel not those stuff under /lib/modules/2.6.24-*/ubuntu directory. So, this is not the answer.

I am looking for a documentation explaining how the maintainers of `linux-ubuntu-modules-2.6.24*' get the stuff under /lib/modules/2.6.24-*/ubuntu directory such as the following one:

acpi/acer_acpi: http://code.google.com/p/aceracpi/
char/intel-agp-ich9m: ...........................
block/drbd: ..............................

If the external source doesn't have any explanation as to the purpose of the module, the list should contain it because the maintainers know what they are doing. So, I expect something like:

acpi/acer_acpi: http://code.google.com/p/aceracpi/
char/intel-agp-ich9m: ........................... (this module is used to ....; the external source doesn't explain this because this is contributed directly by Intel)
block/drbd: ..............................

To Sam: Thank you for the pointers. They really help.

See: https://lists.ubuntu.com/archives/kernel-team/2009-August/006769.html

Thanks Sam, that solved my question.