This is a compilation of many of the different keyboard, trackpad and mice solutions available. It is not exhaustive. If you don't find what you want, search for it.

Drivers
ALPS Trackpad driver - find it here and another here

Enhanced Apple PS/2 driver - find it here

Hacked Apple PS/2 driver - find it here
Keyboard Bindings and Layouts
Key Bindings - Change a few keys on your keyboard. Read this and this.

Key Bindings - Adjust sound volume up/down with Function keys using a method from Stravaganza.

Keyboard Layout (ABNT2) - Brazilian Portuguese. Go here.

Keyboard Layout (PT PT) - Portuguese. Go here.

Keyboard Layout - Make Your Own - use Ukelele. Go here.
Keyboard Shortcuts
Shortcuts available - Read this and this. You can also go to the Help menu in Finder and search on "shortcut lists".

Modify your shortcuts by going to:
System Preferences -> Keyboard & Mouse.

Change Modifier keys in Keyboard tab and change shortcuts in Keyboard Shortcuts tab. For the adventurous, review the Key Bindings entry.
Hot Keys - Many apps like Quicksilver, Butler and Proxi can set up hot keys to perform all sorts of things.
Volume control - control your volume with hot keys using an app and these Applescripts.
Keyboard & Trackpad don't work
Repair Permissions - Try the following:
Boot from install DVD and enter the installer. Select Terminal in the Utilities menu and type:
cd "/Volumes/(name-of-OSX-partition)"   <--- use quotes if name has spaces
                                                                                   
- but don't use parentheses
diskutil repairPermissions ./
cd System/Library
rm -rf Extensions.mkext Extensions.kextcache
cd Extensions
find ApplePS2Controller.kext -type d -exec chmod 755 {} \;
find ApplePS2Controller.kext -type f -exec chmod 644 {} \;
chown -R root:wheel ApplePS2Controller.kext
Quit Terminal and the Installer and Reboot without the DVD
Kext Unload/Load - If repairing permissions above doesn't help, then try to modify the boot script by adding commands to unload and then reload the kexts.

Try the following:
Boot from install DVD and enter the installer. Select Terminal in the Utilities menu and type:
( -- use quotation marks in commands as shown below --)
( -- going to use some variables to cut down on typing --)

dp
="/Volumes/(name-of-OSX-partition)"   <--- use quotes, no parentheses

nano
"$dp/usr/bin/nano $dp/etc/rc.local"
kp
="/System/Library/Extensions/ApplePS2Controller.kext/Contents/PlugIns"
kextunload
"$kp/ApplePS2Keyboard.kext"
kextload
"$kp/ApplePS2Keyboard.kext"
( -- press Command-O to save --)
( -- press Y and <Enter> to accept --)
( -- press Command-X to quit --)
Quit Terminal and the Installer and Reboot without the DVD
ATI Xpress 200M - According to Prasys, the USB Driver creates a confusion that disables the onboard trackpad and keyboard. To fix it, drop his kext onto your Desktop and go to Terminal and type:
cd /System/Library/Extensions
sudo mkdir usb_backup
( -- give password -- )
sudo cp
-Rf IOUSBFamily.kext usb_backup/
sudo cp
-Rf ~/Desktop/IOUSBFamily.kext ./
sudo chown
-R root:wheel IOUSBFamily.kext
sudo chmod
-R 755 IOUSBFamily.kext
cd
/System/Library
sudo rm
-rf Extensions.mkext Extensions.kextcache
Reboot
PS/2 Keyboard and USB Mouse - disable 2 kexts as follows:
Boot your install DVD and go into the installer. Select Terminal in the Utilities menu and type:
cd "/Volumes/(name-of-OSX-partition)"   <--- use quotes if name has spaces
                                                                                   
- but don't use parentheses
cd System/Library
rm -rf Extensions.mkext Extensions.kextcache
cd Extensions/ApplePS2Controller.kext/Contents/PlugIns
mv ApplePS2Trackpad.kext ApplePS2Trackpad.kext.bak
mv ApplePS2Mouse.kext ApplePS2Mouse.kext.bak
Quit Terminal and the Installer and Reboot without the DVD