that's what Xeni at boingboing says, and I totally agree: blocking is futile, information wants to be free and all that.
The mirror list at http://anonymitaet-im-inter.net/wiki/wl-mirror seems well-updated.
My recommendation: also check out the Tor Hidden Services for wikileaks/cablegate (only a few so far, but that'll surely change - in this case Tor is great because it also protects/hides the mirror operator).
The ones I know of right now:
- http://gaddbiwdftapglkq.onion/ (a bit intermittent)
- http://suw74isz7qqzpmgu.onion/ (a bit intermittent)