This used to be a non-trivial operation, the user needing to know which files to copy and so on. The program unetbootin automates the process of creating a bootable USB image from most linux distributions. The program can be downloaded from here:
Most of the major linux distributions (and then some) are included in the drop down menu, however I was pleasantly surprised when I discovered that unetbootin also supports VMWare ESX. Maybe I shouldnt have been surprised, considering that ESX is built on a linux OS, but it worked very well without any modifications.
I simply selected the vmware ESX ISO and after the wizard finished I had a working, bootable USB stick containing ESX server. Useful when the server doesnt have a CD/DVD ROM drive
I also tested with the latest ubuntu desktop 9.10, and it also worked like a charm. Other USB creating programs gave me the problem that during installation the OS would look for install files in the CDROM, which obviously wasn’t there. The UnetBootIn doesn’t seem to have this problem at all…. kudos!
PS – of course your machine must support booting from USB… most machines do nowadays