The easiest way is to not make a "site" but a collection of files which can be distributed by others. You could possibly include offline-executable content, or if you must have it be online (some kind of transactional thing), make it easy to set up mirrors, especially for people to set up mirrors without your cooperation or awareness.
The hierarchy of resilience:
It's trivial to censor an (average wealth, average risk tolerance) individual -- just harass and prosecute for unrelated things. Everyone is a criminal, once you have enough laws...
It is fairly easy to censor a commercial organization (just cut off their payments and banking...)
It's harder to censor a free site (it can do what everyone is suggesting here; hosting offshore, non-US domain name, etc.)
It is much harder to censor something which can be readily mirrored by others.
It is very hard to censor distribution of a dataset. Even harder if the dataset is very small (sony keys, dvd-css, etc.)
It's almost impossible to censor an idea.