Suddenly, as this was being written (10:00pm Friday Melbourne time), http://18.104.22.168/ has suddenly become available, yet it responds to neither traceroute nor ping. According to the cablegate subsite referenced via this address, the release count of US documents is up to 667.
Further research is yielding a few more valid addresses:
In addition, third-party sites are starting to re-publish the information, for instance: http:// http://cablesearch.org/
For those interested, Amazon has released a statement explaining why they terminated Wikileaks.
In addition, all cablegate material released up until yesterday is available via a torrent.
As this evolves, keep searching Twitter for updates via #Wikileaks and #Cablegate.