I've been on other forums where liberals and conservatives debate the issues. Liberals use wikipedia as a source, but I've also noticed that when I find something that helps me make my case and reference an entry at wikipedia...the liberals will then discount it as an unreliable source or just say that the particular item was biased.
I've also notice that when I've found useful info at wikipedia that's controversial to liberals...sometimes a "neutrality warning" label later appears at the wikipedia entry that I referenced.
I usually use the search box at the main page and search for what I'm looking for. (http://en.wikipedia.org/wiki/Main_Page
There is some controversial info that liberals took issue with, for example, on entries related to "Nation of Islam" , Malcolm X, Hamas.
http://en.wikipedia.org/wiki/Nation_of_Islam
(read the entries from the bottom of the page and upward to get a good grasp of some really controversial stuff!)
http://en.wikipedia.org/wiki/Malcolm_X
(the remarks Malcolm X made when he was taking pleasure over the assassination of President Kennedy were disgusting)
http://en.wikipedia.org/wiki/Hamas
If you really want a good laugh take a look at what the atheists have done with the creation and evolution entries, not to mention the constantly changing definition of "Theory".