The GNU/Hurd boxes are only available for people who have already shown some level of involvement in the project. If you simply want to try the Hurd, the easiest way is running it in a virtual machine.

An alternative to online shell access may be using a QEMU image.

Hoster Name Distribution Machine Specs Comments
sceen darnassus Debian GNU/Hurd Xeon E5-1620 3.6 GHz, 1.8 GiB KVM guest on dalaran; public Hurd box; web server
sceen ironforge Debian GNU/Hurd Xeon E5-1620 3.6 GHz, 1.8 GiB KVM guest on dalaran; Debian buildd only, no public access
sceen exodar Debian GNU/Hurd Xeon E5-1620 3.6 GHz, 1.8 GiB KVM guest on dalaran; Debian porterbox, all Debian Developers have access
sceen dalaran Debian GNU/Linux Xeon E5-1620 3.6 GHz, 64 GiB ECC KVM host
libav x86_32-hurd-gcc-4.7 Debian GNU/Hurd libav instance of the FATE Automated Test Environment

If you are a Debian Developer, you can log into the exodar.debian.net machine with your DD account, your public ssh keys are already there. Debian maintainers can also request an account.