After a few days of playing with my Unbuntu installation I finally found the automatic login options: For Hardy Heron 8.04.1
System->Administration->Login Window
Local Tab — Changes look
Security Tab — Allows auto login
Nice, but when I rebooted I was just given an equally annoying prompt which asked for my keyring password. I found this answer in this forum post. You can just delete your unlock password entirely.
System > Preferences > Encryption and Keyrings
Under Password Keyrings click on “login Automatically unlocked when user logs in.”
Click “Change Unlock Password”
Enter your old password, but leave the new password blank.
And now you have a normal insecure auto-login.