Lots of forks, as in Protestant churches (http://nl.wikipedia.org/wiki/Bestand:Gereformeerd.svg really starts to look like a history of Unix)

Of these http://en.wikipedia.org/wiki/Mennonite_Church_in_the_Netherl... probably would be popular; every church member writes his own confession when joining the church.

Probably Judaism.

Seriously, I think the Jews invented the wiki: consider the form and structure of the rabbinical commentary on their holy texts, very wiki-like in form and purpose. Of course ordinary believers couldn't "edit" it...

New Age?

Unitarian Universalist?

Not trying to be rude, these are merely the most obvious cases that mold themselves to the believer's opinion. Also, observe the syncretism of Buddhism in different regions.