Start here:

http://wiki.eeeuser.com/ubuntu_9.04

Next:
http://rhau.se/2009/03/27/ubuntu-904-on-the-asus-eee-pc-1000h-with-acpi-and-wifiwlan-working/

And:

http://blog.bokhorst.biz/1712/computers-en-internet/installing-ubuntu-jaunty-jackalope-asus-eee-pc/

And:
http://www.informatik.uni-bremen.de/~elmurato/EeePC/

And:
http://www.jpierre.com/2009/04/installing-ubuntu-netbook-remix-904-jaunty-jackelope-on-eee-pc-the-howto-guide/

And:

http://forum.eeeuser.com/viewtopic.php?pid=566834