Ubuntu 13.10 (Saucy Salamander) was released today, so we have just added the amd64 and i386 server edition installable ISOs to our collection so that new installs can take advantage of the latest release.
Note that Ubuntu will be providing maintenance updates for Ubuntu 13.10 for 9 months, until July 2014. If you need long term support we recommend you install one of the LTS releases of Ubuntu instead.
For more information, have a look at the release announcement here, which contains plenty of useful info, including about upgrading from 13.04 if you are running that.