Clones: general wiki encyclopedias with different administrators than Wikipedia.
Mirrors: no, but there is no restriction on manually copying large quantities of information from Wikipedia.
Different content: nothing necessarily different.
Conservapedia: sure, it's a good thing, but not something I would personally support.
I donated to Wikipedia before. However, this year, I'm not donating, and my rationalization is this: there need to be more Wikipedia clones on the internet, to best prevent the possibility that a single organization (Wikimedia) abuses its control of the biggest worldwide information source. Thus, instead of donating to Wikipedia, I would like to subsidize potential Wikipedia clones. Whether or not it has ads is of little concern to me.