Updated for ESXi 4
If you have a linux box and a 1 gig thumb drive, here is how to install VMWare ESXi onto that drive in 2 commands. Download the ESXi ISO and then mount it in linux like so
mount -t iso9660 -o loop VMware-VMvisor-Installer-4.0.0-171294.x86_64.iso /mnt/esx
Now we’re going to write the installer file to the thumbdrive. I’m assuming the thumbdrive is /dev/sdb
tar xvzf /mnt/esx/image.tgz usr/lib/vmware/installer/VMware-VMvisor-big-171294-x86_64.dd.bz2 -O | bzip2 -d -c | dd of=/dev/sdb
This will take a little bit, but once it’s done you’re good to go. pop that drive into a USB boot capable board, configure your storage and away you go!