You should use soft like Gscraper or Scrapebox to find wikis and then check PR. Just google "wiki sites footprints" to find out more about scraping. Also you can find ready lists of such sites on forums. Again google is your friend
You can find many option on Google for wiki site list, but I will recommend http://webtrends.about.com/od/wikilists/tp/list_of_wiki_sites.htm this list, which I have already used. Hope it would be helpful for you.
Maybe the "Search" function would not be a bad idea next time when asking such questions while there are AT least 10+ topics about the same thing... Also Google it next time