The following URLs were incredibly useful in writing this HOWTO and generally getting ACPI up and running.
HOWTOs
http://tuxmobil.org/howtos.html You'll need to scroll a bit, or use the HTML version: http://tuxmobil.org/Mobile-Guide.db/Mobile-Guide.html
http://tuxmobil.org/Mobile-Guide.db/mobile-guide-p2c1-hardware-in-detail.html
Hardware-specific Install Reports and Info
http://acpi.sourceforge.net/wiki/index.php/InstallationReports
http://acpi.sourceforge.net/dsdt/index.php Includes links to patched DSDTs and HOWTOs about patching your own DSDT.
http://help.nec-computers.com/au/pri/item_instr_bios_7521N.asp
Software Development Groups
ACPI articles
http://www.analog.com/library/analogDialogue/archives/34-04/fan/
Mailing List Threads
http://lists.debian.org/debian-laptop/2003/debian-laptop-200304/msg00367.html
http://lists.debian.org/debian-laptop/2002/debian-laptop-200212/msg00242.html
ACPI packages and related software
Remember to choose "F" for full when you download your kernel source. http://www.kernel.org
maxx's pre-patched 2.4.20-8 kernel source package. For more information see maxx's notes. http://people.debian.org/~maxx/kernel-source-2.4.20/
You'll need to pick the version that exactly matches the kernel you're using. http://sourceforge.net/project/showfiles.php?group_id=36832
the daemon http://sourceforge.net/projects/acpid
text interface http://grahame.angrygoats.net/acpi.shtml
graphical interface for KDE http://www.elektronikschule.de/~genannt/kacpi/download.html
another KDE interface http://akpi.scmd.at/
WindowMaker DockApp (another GUI) http://www.ne.jp/asahi/linux/timecop/
WindowMaker DockApp (another graphical interface). Handles two battery slots. http://open.iliad.fr/~clecourt/wmacpi/index.html