Update 11/12/2008: New PostInstallPackage version (V 0.6) —> corrects problems with the display of remaining battery time after sleep
Update 11/28/2008: New PostInstallPackage version (V 0.7) —> SpeedStep files, Bluetooth kexts, new 10.5.5 GMA kexts with brightness control
Update 12/01/2008: New OPTIONAL PostInstallPackage version (V 0.8) —> Added the Old brightness fix as the new one seems to break some installs, added README to the OPTIONAL with description on how to recover from bad kexts.

1) BIOS Update to fix ACPI Problems

1a) Update from XP

The simplest way to do a BIOS Update - use Asus Windows Tool and Run update from file
BIOS Update is always a risk - for me, all went fine and the long boot time was fixed!

• Get modified Bios from: osrom.net
• Run ASUSUpdate
• 
• Select "Update BIOS from File"
• 
• Select the downloaded file
• Follow the steps to update your BIOS

1a) Update natively

To flash the BIOS,

• Rename the ROM file to whatever the name of your comp model is, in my case 1000.ROM (or 901.ROM)
• Put it alone on a USB drive and insert it into your computer. Reboot, hit F2
• Under the Boot tab of BIOS settings, change priority boot device to USB drive
• Go to exit, select exit + save changes
• This will cause the comp to reboot again, so as soon as you see it start up, HOLD DOWN alt + F2
• This will go into EZ-FLASH and update your BIOS
• Reboot, hit F2, double check that BIOS is working

2) Partition your Harddisk

In this example we keep a dualboot configuration with XP (first partition) and OSX (second partition).

In order to accomplish this you'll have to do some slight changes in your partition scheme.

I'll recommend you do a complete backup of your harddisk before continuing!!!
You can use programs like GParted (free) or Acronis Disk Director to do so.
The following shows the method using the (still) installed XP to partition your disk:

• Right click on "My Computer" on your desktop and select "Manage"
• Then click on "Disk Management"
• 
• 
• Delete the second partition by right clicking on the second partition of Disk0 and selecting "Delete Partition".
• 
• Create a new unformatted primary partition
• 
• 
• 
• 

3) Installation

3.1) Preparation - Downloads

• Download iDeneb 1.3 10.5.5 from the usual sources
• Burn it to a DVD

3.2) BIOS Settings

• Enter BIOS Settings by pressing F2 at the gray boot screen
• Go to Advanced - Onboard Device Configuration

Onboard LAN: Disable 
Onboard Camera: Enable 
Onboard Wlan: Enable 
Onboard Bluetooth: Enable 
Advanced - CPU settings

Max CPUID Value Limit: Disable 
Hyper threading: Disable (If you have it in the BIOS - mainly for 901 users) 
Intel Speedstep Enable (If you have it in the BIOS - mainly for 901 users)

• Save & Exit

3.3) Installing OSX

• Put the iDeneb 1.3 DVD in your external DVD drive and boot from it (Hit ESC at the gray boot screen and select your DVD drive in the blue/yellow list)
• The boot may take a while (5-10 minutes depending on your DVD drive)
• 
• 
• 
• Just click through until you come to this screen
• 
• Run "Disk Utility"
• 
• Select the second partition that you have created in step 1 and format it by selecting "Mac OS Extended (Journaled)", naming it (OSX in my case) and hit "Erase"
• 
• 
• 
• To be sure you can select the drive and select "Partition". Press Options and you should see that the drive is partitioned as MBR$
• 

• If you go back now you should see something like this.
• Select the drive and click "continue"
• On the "Install Summary" Screen click "Customize"
• 
• Select the following options:
  • Chipsets and check ICHx Fixed..
  • Fix and check FireWire Remove
  • Video/Intel. Finally, check the box for GMA950.
    • 
    • 
• I recommend you install some useful tools:
• 
• Hit "Done" and "Install"
• Go have a coffee or two, install takes around 25 - 40 minutes.

3.4) Post-Install

After first boot you'll have to answer some questions to Apple. Don't forget to define a password, we'll need it later!
Get the post install pack here(7MB) and the OPTIONAL post install pack here(7MB) (I compiled a configuration that worked for me. I take no credit at all for this. Guys like paul over here did the lions share of the work).
Unzip the downloaded file (normally it unzips to the same folder)

There is no guarantee that all the kexts in this bundle do work with your eee PC.
There are simply too many different hardware revisions out there 
(even on the 1000h it seems that there are at least 3 different brands of the camera used - some work, some don't).

So if you install the kexts: 
 - Do so by following the guide (unless you know what you're doing) as it makes it easier to spot an offending kext.
 - Install them using kextHelper (it sets the corrects rights and stuff and makes a backup of your replaced kexts).

If ever a kext has your system carshing/not booting/unstable do the following:

- Boot into "single user mode" by specifying -s at the boot prompt
- Then type:
      /sbin/fsck -fy 
      /sbin/mount -uw /
            (don't forget the / at the end!!)

- Then erase the offending kext(s) with the backup(s) (example of AppleIntelGMA950 kext)
      cp -R /Backup\ Extensions/AppleIntelGMA950.kext/ /System/Library/Extensions/
      rm /System/Library/Extensions.mkext

- Reboot with the -f option

3.4.1) Fixing "About this Mac"

• Install the "About this Mac" package. Just click through it
• 

3.4.2) Installing kexts

• Run "Kext Helper"
• 
• Drag all kexts in the "kexts" folder onto the "Kext Helper" application
• 

• Type your password, click "Easy Install" and follow the dialogs
• Reboot

Remark: Installing the IONetworkingFamily.kext fixes Time Machine but seems to break the Ralink Wireless driver!!!

3.4.3) Fixing the resolution (might not be needed on some models)
It's possible that you'll have a strange 800x600 resolution. Don't worry, we'll fix that.

• Install "SwitchResX"
• 
• Launch "SwitchResX" property panel
• 
• Go to "Custom" and click on the plus sign "+"
• 
• Create a custom resolution. Only change the "Pixel Clock "to 60 and the Horizontal resolution to 1024 and hit OK.
• 
• Click "Apply"
• Launch "OSx86 Tool"
• Select "Enable/Disable Quartz GL"
• Click on "Enable Quartz GL"
• 
• Reboot

3.4.4) Fix Power Management

• Delete the "PowerManagement.bundle" in System/Library/SystemConfiguration by dragging it to the Trash (it might be a good idea to make a copy first ;-). You'll have to enter your password to proceed.
• 
• Now install the new "PowerManagement.bundle" by dragging it to System/Library/SystemConfiguration. Again you'll have to enter your password to proceed.
• 
• Launch "OSx86 Tool"
• Select "Repair Permissions" and "Clear Extensions Cache"
• Click on "Run Selected Tasks". You'll have to enter your password to proceed.
• 
• Wait (this may take some time - 5 to 10 minutes)
• Reboot

3.4.5) Install WLAN Driver if you stayed with the original Ralink card

• Download here
• Use specific application to control WLAN
• I for my part installed a Apple Airport mini PCI WLAN card - BroadCom BCM 94321MC 802.11n (search for BCM94321MC on eBay - around 20$-30$)
• which works out of the box and is recognized as Airport card.

3.4.6) Fix sound
See this wiki entry for making sound work (or follow the included SoundHowTo.rtf document).

3.4.7) Brightness Control

• Double-click sleepwatcher_2.0.5.dmg in the OPTIONAL/Brightness Control Fix folder
• Install both packages
• Now you have two choices (the 10.5.4 should work on all eee PCs, the 10.5.5 seems to hang on some but is optimized - in case of problems refer to chapter 3.4):
• Either install AppleIntelIntegratedFramebuffer.kext with kextHelper from the 10.5.4 folder
• Or install AppleIntelIntegratedFramebuffer.kext and AppleIntelGMA950.kext with kextHelper from the 10.5.5 folder

• copy the two rc files to /etc
  • Open terminal
  • Go to the folder where you unpacked the PostInstallationPackage (something like /User/YOUR_NAME/Desktop/MY_BUNDLE_VX/OPTIONS/Brightness Control Fix folder
  • Type ./install.sh
  • Type your password
  • Type sudo reggie_se -x -D PentiumM
  • Get the line number where it says "Display controller: display" (should be 16 or 18 or something like that)
  • If you don't get 16 (which is the value that worked on my 100h), open the two rc.* files and adjust the value for the -i parameter (reggie_se -D PCI -i 16…)
• Reboot

3.4.8) SpeedStep
Thanks to Slither2007 for this guide.

* Install these two files from the Optional Post Install Package (V0.8 or later)
o GenericCPUPowerManagement Kext (make sure to get the 1.0 version, the new one does not work)
o GenericCPUPowerManagement Application

* Unzip them in your Documents folder.
* Use KextHelper7 and install the kext.
* Copy the App into your Applications or Utilities.
* Add the App as a Login Startup Item and tick the Hide box.
* Restart PC and enjoy!

That's it…

What works: 
- System running with EFI, vanilla and Quartz extreme support 
- Stock Kernel : working with EFI 
- GMA950 : working with QE & GL 
- Sleep Mode : working 
- Sound output working 
- Wlan : working (After Start and wake on Powersaving a manual switch off/on is needed on original Ralink Card) 
- Camera: : working 
- Multitouch : 2 finger scrolling, 3 finger control, 2 finger doubletab 
- SD Slot 
- External USB to Ethernet adapter for the MacBook Air 
- Time Machine
- Brightness control (using [http://ipis-osx.wikidot.com/, over here])
- Speedstep 

What does not work yet: 
- Sound input (microphones) not working 
- Ethernet 
-- Speedstep--

List of components in the Post Install Pack
Post Install Pack here(7MB)

List of components in the OPTIONAL Post Install Pack
Optional Post Install Pack here(5MB)

There is no guarantee that all the kexts in this bundle do work with your eee PC!!!! See section 3.4 for troubleshooting instructions.

All the information in this post comes from the following sites and from hours of trial and error work from my eee PCs:

http://forum.insanelymac.com/index.php?act=idx
http://ipis-osx.wikidot.com/
http://www.maceee.com/
http://eeepc-osx.wikispaces.com/901
http://wiki.taruga.net/