http://wiki.cyanogenmod.com/index.php?title=Fastboot
Used these instructions to unlock the boot loader of the Nexus One.
http://wiki.cyanogenmod.com/index.php?title=ADB#Linux
I installed the udev rules from this page on Ubuntu to get the HTC Google Android Nexus One properly recognised by Ubuntu.
http://developer.htc.com/adp.html
I downloaded fastboot from this page for the HTC Google Nexus One.