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Earlier, WikiLeaks tried to employ Amazon's Web Services to enhance the site's stability and protect itself from DDoS attacks, but that didn't last long, as Amazon quickly dropped WikiLeaks from its servers.
WikiLeaks currently exists on the web only in the form of (mostly partial) mirrors, some of which can be found at wikileaks.info.
Update: WikiLeaks has announced it moved to Switzerland and is currently available at the address wikileaks.ch. The address is resolved to a numerical IP, which means WikiLeaks still hasn't fixed its DNS-related issues.