ICS for virtualbox:

Installer vdi:

Instalation description:

VirtualBox settings:

• Procesor - enable PAE/NX
• network adapter - NAT
• New disk - IDE Primary master ~2G
• Installer vdi - IDE Primary slave
• Sdcard - IDE Secondary master

Instalation:

1. After booting VBox instance press F12 key to display boot menu.
2. Then choose "2) Primary Slave" to boot from instalation disk.
3. Then quickly select "Android Install to /dev/sda from /dev/sdb." (you have 3 seconds until automatic boot from sda)
4. After first installation reboot virtual machine. (some instructions recommends that you may repeat steps 1-3, but I think it's not neccessary)
5. Installation is complete, but sdcard is not mounted (I'll write instructions soon)

Links:

• Build and installation instructions (Japanese)
• Running Ice Cream Sandwich in Virtualbox, two parts (English)