This video shows how to install openWRT 10.03 in VirtualBox.
The video also shows how to configure the network file so that openWRT can connect to the internet and also shows how to configure GRUB to boot without delay.
The end of the video shows openWRT booting in 3 seconds.

For copy and paste reasons, here are the commands that you can use to get openWRT 10.03 installed in VirtualBox.

Boot Ubuntu, run:

sudo -s

Then download openwrt with:

wget http://downloads.openwrt.org/backfire/10.03/x86/openwrt-x86-ext2.image.gz

Then:

gunzip openwrt-x86-ext2.image.gz

And to install:

dd if=openwrt-x86-ext2.image of=/dev/sda bs=1M count=100

Once that’s done (should take less than two seconds) openWRT will boot, but to fix an annoying issue that means you have to wait for ages for GRUB to load you can do:

fdisk /dev/sda

when in fdisk press v [enter] and then w [enter]

Then:

mkdir grub && mount /dev/sda1 grub

And now edit the GRUB configuration file with:

nano grub/boot/grub/menu.lst

Now remove the first lines of the file so it starts:

default 0

and change timeout to 0

Once that’s done you can type

reboot

and enjoy openwrt.

p.s. when in openwrt to get an internet connection do:

vi /etc/config/network

and change

option 'proto' 'static'

to

option 'proto' 'dhcp'

and reboot